Why can't I access some websites?

[SCArt]

For the past week I have been unable to access certain websites - they are all standard sites (i.e not dodgy) some of which I usually access regularly (eg Sainsburys) and some which I have rarely or never accessed before (eg National Trust Photo Library www.ntpl.org.uk)

Some sites I can access if I type the URL in directly but not if I do a search and then click on the relevant result si its not a problem with the sites themsleves.

I am using the latest version of Firefox but see the same problem in IE. I have wired 10 MB fibre optic broadband from Virgin Media and for the sites I can access it is very fast (I have had it for about a year without any previous problems)

I have done the following to try and resolve it:

1. Virgin (to their credit) came and replaced the modem and ethernet cable and checked the signal, which is good.
2. I have done an ipconfig /flushdns (In case the DNS mapping wasn't right)
3. I have done a scan with StopZilla (no infections found)
4. I have cleared all internet history, cookies, cache etc
5. I have cleared all temporary files and generally cleaned up my PC

In addition sometimes a Google search doesn't work - just hangs.



In all cases the Firefox tab just shows "connecting" and the little green circle going round (that's techno-speak for you) - it never comes up to say it couldn't find the site or failed to connect - just sits there for up to an hour before I get fed up and close the tab down. I might then try typing in the URL and get to the site (or I might not)


My PC is 5 years old and running Vista (arghh)



Is there anybody out there with any good advice on what might be going on ?


Many Thanks

 

[Montaigne]

Have you got virus protection on your PC? Have you scanned your pc for virus's if you have?

Do you have a firewall running? Have you recently installed/activated a firewall or some form of virus protection such as Norton or Kaspersky?

It could be that the firewall is blocking access to certain sites. If you have such a thing check that these sites are not in the Blocked section of the firewall.

 

[SCArt]

I am using StopZilla for virus protection - and it has found no infections.

It can't be the firewall blocking certain sites because I can get to them (sometimes) by typing in the URL directly. I can also get to some sites but not to some of their deeper pages.

The only change to virus protection I have made recently was to disable McAfee as my PC was generally running very slowly and I was advised that having 2 anti-virus tools running real-time protection can slow things down as they both compete to check files.

 

[mattk]

HAve you tried changing your DNS settings to something like OpenDNS?

This article explains it in simple terms.

 

[Sparx]

What version of Firefox are you using? But yes, highly recommend you setting up your PC to use OpenDNS' servers.

 

[KM-Tiger]

But why change DNS when there appears not to be a problem with DNS. If there was, Firefox would hang on "Looking up ...", rather than the "Connecting to ..." the OP reported.

Could be an odd routing or MTU issue, both are hard to diagnose.

Is the problem the same if you use a different browser?

 

[InPrintImaging]

There are one or two viruses that exhibit this sort of behaviour and they can also attack your antivirus software so that it won't stop them, or even alert you that you have an infection. Boot in "safe mode with networking" and then down load the Malwarebytes anti malware program (the free edition). Run it and see what happens. You could also try Spybot search and destroy. Unfortunately situations like this can get ugly (and beyond my computer skills), but that is where I would start.

I had a very serious issue similar to this a couple of years back, and AVG was completely useless at fixing it. Since then I have been using ESET smart security, and although it isn't infalible, it does seem to stop more of these problems.

 

[mit74]

check you MTU settings on your router. Try lowering it to 1432.

 

[That Guy]

Running any Ad-Block Browser Plugins?

 

[webstore]

If you get problems reaching a given site, try using your mobile or another PC that uses a completely different broadband provider. It might be your current provider has a DNS problem that's not resolving your URL request.

As somebody else has suggested here you could try another open DNS service but that's more fiddly to try than the above suggestion.
.

 

[Subbynet]

Try a LiveCD - like Ubuntu. See if you can access the sites with it.

This should help show if its a software or hardware based issue.

 

[mattk]

But why change DNS when there appears not to be a problem with DNS. If there was, Firefox would hang on "Looking up ...", rather than the "Connecting to ..." the OP reported.

Could be an odd routing or MTU issue, both are hard to diagnose.

Is the problem the same if you use a different browser?

Using OpenDNS will take that out of the equation.

It very much sounds like a virus to me.

 

[SCArt]

Thanks for all the replies - sadly the gremlins in my PC did not go away when I left them alone all week-end and I have had problems connecting to this site this morning.

I think "inPrintImaging" may be right and it is a virus issue because this morning StopZilla did detect an infection and is now running a full scan (intelligent scan was run previously)

If that is not the cause I may try using OpenDNS - although there isn't an obvious problem with mapping I did see some strange effects when I type in the IP address of a site I know and it came up with microsoft's IIS site - could be some changes have been made but strange all the same.

I'm not running any Ad-block plug-ins but have read elsewhere about changing MTU settings so may give that a try if StopZilla doesn't sort it out.

One last thing (seems unlikely, but...here goes) - a few months ago my external NVIDIA GeForce 7300 LE graphics card had some sort of problem and I switched to using the integrated graphics card which has been fine for several months but recently on a reboot the PC woouldn't boot up and gave an error message something like "You are using the integrated graphics card but this PC is configured to use an external card".

So I switched the cable back to the external card (which previoulsy hadn't worked - blank screen) and it all started working fine. But it was from around that point that my current troubles started - could it just be a coincidence???

 

[Tony221268]

A very brief survey of the symptoms makes me guess that it might be a corrupted hosts file. There is quite a bit of nastyware that plays with a file in

Windows/system32/drivers/etc

Browsers will check this file and if they find an entry will divert any search for that site somewhere else. If it directs it to a non-existent location it might hang.

Without being at your pc it is very hard to say how good my guess is. Either way try anti-malware products like CCleaner or Search and Destroy.

You can manually learn how to repair your hosts file (lots of Google info on that: type "default windows hosts file" or "repair hosts file windows").

Also ensure updates are on and that you have good anti-virus/ malware software installed.

 

[Tony221268]

One last thing (seems unlikely, but...here goes) - a few months ago my external NVIDIA GeForce 7300 LE graphics card had some sort of problem and I switched to using the integrated graphics card which has been fine for several months but recently on a reboot the PC woouldn't boot up and gave an error message something like "You are using the integrated graphics card but this PC is configured to use an external card".

So I switched the cable back to the external card (which previoulsy hadn't worked - blank screen) and it all started working fine. But it was from around that point that my current troubles started - could it just be a coincidence???

I really doubt that it has anything to do with this. Be like blaming a tyre change for the sat nav going wrong.

 

[SCArt]

Thought the video card thing seemed unlikely...

Since my last post I have become convinced it is a virus as Stopzilla again picked up viruses/trojans and I also used Malwarebytes which picked up more that Stopzilla had not detected. McAfee meanwhile detected nothing!

Am going to try doing a major cleanup (found detailed post on a tech forum) but just getting laptop set up as a full working backup machine in case it all goes horribly wrong. If it all goes well I will post a link to the tech forum post for anyone else who is experiencing something similar.