I'm afraid this does sound like a malware / virus issue. Lots of malware will attempt to block you from downloading security / updates which might interfere with what the virus is trying to do.

Please see the steps here:

http://windows.microsoft.com/en-gb/windows/how-remove-computer-virus#how-remove-computer-virus=windows-7

The steps are for windows 7 but any differences for XP are mentioned in the article.

You will probably need to boot Windows into Safe Mode with networking and then download and run scans from there.

You should scan with your existing antivirus (after complete definitions update) but also try with other separate tools. Malwarebytes (once updated) is a good place to start but you can also try the following:

• Microsoft Safety Scanner
• TDSSKiller - AntiRootkit Utility
• Hitman Pro
• ESET Online Scanner

If you are unable to install / update virus scanners even in Safe mode with networking then you can try a tool like Malwarebytes Chameleon which should get past the virus's block. Or if all else fails (and you really can't get to another PC to download the virus scanners) then you can try an online antivirus scan. One like this:

http://www.eset.com/us/online-scanner/

Please note that I have no experience with these so I am not recommending them. Best to read around before choosing a product to ensure it is reliable / trustworthy.

Once you have found and removed the malware / virus you should be able to restart windows and boot normally. You should then be able to update Firefox and your plugins by following the steps here:

• Update Firefox to the latest release
• Plugin Check and Update page

Further information can be found in the Troubleshoot Firefox issues caused by malware article.

Thank you for your reply, unfortunately I cannot download or update anything in safe mode either, not even the online scanner you suggested...

Are you able to access the internet at all?

Have you tried MalwareBytes Chameleon?

The best option is probably to find another computer. Download / install the antivirus on there and then scan the infected computer from a USB stick. You could use something like the Spybot Portable or AVG Rescue CD

Or you could remove the hard drive from your laptop and plug it into another PC as an external drive and scan it (note that this risks infecting the other PC).

Or you could create a Linux Live CD and run antivirus on the hard drive from there.

I'm afraid that if you can't get any of this to work (sounds like a nasty virus) then there is not much more we can do from a Firefox support perspective. The best bet is probably to contact your laptop manufacturer for support ( especially if you are within warranty).

The last ditch option will be to completely wipe your PC and reinstall windows from scratch. This will get rid of the virus but also all of your personal files, programs, settings etc. Make sure that everything you want to keep is backed up first.

I hope that helps.

Turns out it was a problem with the router/modem, nothing related to malware. I didn't realize it before, but my phone also couldn't download updates or new apps and the computer of a friend had the exact same problems once connected to the wireless network at my house.

Still not entirely sure what caused it but rebooted the modem and router and everything works again.

Thanks for your help anyway, should've tried my phone earlier, maybe I would have figured it out sooner then

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe Mode start window.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Do plugins that you have installed work via links on the test page(s)?

• http://kb.mozillazine.org/Testing_plugins