did you try deleting the firefox profile in AppData folder?

https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data

if you can't reach that page, here is the money quote:

click the Windows Start button and type %APPDATA%, delete mozilla folder there. Note, it has to be all caps.

Yes i did sorry forgot to mention.

This seems beyond firefox, I understand you mention there is no problem with windows firewall, but just for diagnose purposes, can you turn firewall off and see if it helps?

Just tried your suggestion to no avail. Any further suggestions gratefully appreciated, cheers crislevin.

At this time, I don't have any good ideas, but please provide a bit more information so I or others can help further:

1. when you type in the url and press enter, in the bottom left of the browser window, it will have some status notification, it maybe "looking up..." "connecting..." "waiting for response...", "transferring data...", what was the status you get when trying to reach those websites?
2. when you say "can't open", what error page shows up?
3. if you can't open http://www.google.com/ can you open http://74.125.224.72 ? (this is the ip address of google.com, using this directly should bypass DNS issues).

The crazy thing is there is no error message it simply accepts the google url momentarily says connecting on the above tab & then quickly blanks out and reverts to the original page. It's as if it's not even trying to resolve the url. Cache & cookies have been cleared.

http://74.125.224.72 worked fine, good thinking, but tried typing http://63.245.217.105 which is mozilla.org and the same problem occurred. But it does indicate a DNS problem would you agree ?

Possibly. It is hard to understand why other browsers are fine though.

Two things to try:

1. check firefox's options->advanced->network->connections, it should be "use system proxy settings", nothing else should be checked.

2. if above is good, try goto windows TCP/IP settings, and manually add a third part DNS, there are many you can use, check here http://pcsupport.about.com/od/tipstricks/a/free-public-dns-servers.htm

Hi crislevin, I have tried the above to no avail, I've decided to re-install windows because I've been having a few niggling problems there also.

Most of my data is on external drives so it will not be to much trouble. Thanks for all your help.

Psylocke.

Okies, sorry couldn't figure out in the end. If you still plan to install firefox, you can set up a sync to get all your bookmarks/passwords/history/addon to back up, then reinstall windows.

Good luck!

All working fine now.