Done it already (read the rest of the thread)

Is my Firefox problem a result of Malware ?

https://support.mozilla.com/en-US/kb/Is%20my%20Firefox%20problem%20a%20result%20of%20malware

Check and tell if its working.

No. I have 2 up-to-date anti-malware products installed and I've scanned using these several times. I also use Kaspersky Internet Security which reports no problems. I've also used the Kaspersky Network monitor to analyses the network processes running when FF hangs. Other than connection to IP address of the site being visited I can see no other connections. Kaspersky does not report issues.

After nearly 2 weeks of constant hanging I am begining to note a pattern:

Firefox seems to be far more likely to hang on any website that is not straight up HTML content. i.e. any site with active content, banner ads, adsense, social media, media plugins etc... so basically on most sites :(

But apart from that there is no pattern. I can go and revisit a site that it hung on before and site works fine, then all of a suddenluy 20 mins later.. bam.. it's no longer responding while trying to access some other site.

As I said, to date zero crash reports

Well as of today I seem to have temporarily stopped the hangs... basically I've installed Addblock and also BlockSite and banned all content from Googles' doubleclick.net. Also for this article which matches my experiences:

http://www.xtremecomputer.com/tech_articles/google_applications.asp?gdyk=5039

Basically it seems FF5 is having major problems with many add networks, social media plugins etc... I really hope they get these issues fixes soon as obviously if everyone excludes banner advertsing then we have a major problem!

I wish I had the time to take this further and try isolate exactly what the issues are here, as what I've done is a HUGE blanket block on so much content, but right now I've wasted many hours with FF hangs and I need to put my time to more productive stuff.

For the techoes reading this I do also notice a lage number of connections being opened by FF even on the safest sites, and often these not being closed later. So I suspects as per the article that FF is hanging when trying to deal with unresponsive connections to 3rd party sites via the site being visited.

I experienced the same problem for the last couple of weeks with Firefox (or Chrome) constantly hanging (usually Firefox says it's "connecting"). Can't kill the process and must reboot (sometimes having to do a manual power off since there is also a problem with nsAppShell (?) not ending). I uninstalled the IObit Malware Fighter and this solved the problem!!!

Been having the same problems myself the past few weeks.

I uninstalled IObit & am not having the problem anymore. Thanks, Zuneplanet.

This bug was a "head scratcher" for a while (too many lengthy and ineffective solutions posted. Decided to uninstall the IObit product since that had been updated in the period when the problem first appeared. Switched to Malwarebytes Anti-Malware, but its free version offers no real-time protection which makes me nervous!

I'm happy to report that IObit's already fixed the bug, Z. You've got to redownload it, and then replace a couple of files in the program folder with the ones available here:

http://forums.iobit.com/showpost.php?p=65648&postcount=14

Arg - I spoke too soon. I have a couple of browsers, and it fixed the problem on one, but not FF. The new Spybot has live protection, so I'm using that 'til they get this fixed.