Thanks for the reply.
Since last post I tried something. I had only disabled zone alarm, and the problem persisted. So I did an uninstall, and the problem hasn't come back in over a week. Fingers still crossed. Still using the Vista built in firewall, and now gunshy about a switch.

Thanks for making this post. I have been using Zone Alarm for years, and never thought that this program could cause this kind of a problem. Will try removing it and installing comodo which I put on a friends computer last month. Worth a try, since I have had the browser stalling problems for quite a while now. If it works, will try reinstalling comodo on another friends machine.

I too have had the same problem. Using:
An HP 8530w laptop with windows vista business 32bit, SP2;
AVG Free up to date,
Spybot S&D up to date.
The problem only started in the last 3 / 4 months, and seems to occur with any of the 3 browsers I have installed (Firefox 3.5.2, Google Chrome and IE7): Browse for a while, then browse no more. The browser seems fine - just that websites won't load.

If I try do something like download a torrent through utorrent - it works just fine. (Is only port: 80 affected?)

So now I close the browser - File > Exit or click the X, and it closes. Restart firefox and I get the 'Firefox already open message'. Chrome and IE will open again but still not load pages.

Firefox cannot be terminated in my task manager - no matter how many times I try. Rebooting / Shutting down takes 10minutes, so I (unhappily) resort to a forced shutdown (hold in power key).

What I've done:
Updated my BIOS - this made no difference.

I've gone into my BIOS and disabled any ports / hardware I'm not using. Right after that I uninstalled ZoneAlarm (which was inactive since I got annoyed with it but never uninstalled it). Since doing these two things I have not had Firefox freeze on me. I suspect, due to other posts on the issue, that it might well be ZoneAlarm - but I'm not 100% sure what is going on. Pc seems fine for now.

This seems a very common problem and yet there is no obvious solution to it. Seems a bit hit and miss - for some people one thing works for some people another thing works.

I got rid of Zone Alarm in June and installed Comodo instead, and have never had the problem with my browser stalling again, or not being able to restart it. For whatever reason, zone alarm seems to be incompatible with something that was evidently install in a Vista update. I had used Zone Alarm for years, and was reluctant to remove it, but Comodo has proven itself to be a good firewall, and am very satisfied with it. I also have Vista 32 bit O/S.

Update: Firefox continues to work. No problems.

Decided it was time for a firewall again. Installed Sunbelt Personal Firewall and got the same "Firefox already running..." message after a few days of installing it. The only reason I've not used Comodo (as suggested) is that it comes with Antivirus - & I'm quite happy with AVG Free Edition.

Is Comodo on par with AVG? Worth installing or shall I try a 3rd Firewall

I have had this issue on my Dell Inspiron desk top that I purchased about a month ago. In fact when it happened within the first week of owning it, I returned the machine to the vendor and exchanged it for a new one. Same problems as described by all who have posted...IE stops working but e-mail & Skype work. When IE shuts down, no other program seems to work either. Finally, I also had difficulty shutting down. Through a process of elimination, I finally uninstalled Zone Alarm and so far (last 4 days) I've been doing fine. I am using Windows Firewall instead. I was a long time ZA user with XP prior to this. I am currently running the 64 bit Vista, but using the 32 bit IE8. I'll check back in a few days to report on the status...hopefully it will be good!

I think that Comodo is a better firewall than the one that comes with Windows Vista, and ever since I installed it, I have had no problems with Firefox. You can also install Comodo without the Anti Virus, and that is how I have done it. I use Comodo with AVG 8.5 on my computer, and it works just fine, and I feel that I am well protected. I had used Zone Alarm for many years before the problems with Firefox surfaced, and going to Comodo solved it.

Well, so far so good...since uninstalling Zone Alarm, I have had no recurrences of IE shutting down in the middle of a session and effectively disabling all other operations as well. I'm going to give it another week and install Comodo. In the mean time, I'm continuing to use the Windows firewall.

Does anyone know if ZA will be compatible with Windows 7?

I believe I'm the original poster of this thread. By way of update: the machine in question is still running the Vista built-in firewall, and only IE is used. We no longer use Firefox on that machine, and so far the firewall has done the trick.

No problems since Jan 27th. That's 8 months. I'm disappointed that I stopped using both Firefox and Zone Alarm, because I like them both, but that's the brakes.

I still use Firefox exclusively on my XP machines. Furthermore, I moved and switched to ATT Uverse, which came with a firewall, so I guess this means I'm not using Zone Alarm at all anymore. I got a lot of mileage out of that firewall.

Zone Alarm, that is...

I have been using AVG 8.5, Comodo and Firefox 3.5.3 for the past couple of months, and am not having any hang up problems with Vista 32 bit. Getting rid of Zone Alarm seems to be the thing that cured the problem. I had used Zone Alarm for many years in the past, and it had seemed to work OK with Vista earlier in the year, but Microsoft must have made some kind of change in Vista that finally caused Zone Alarm to be a problem. I think that Comodo is a superior firewall to the one that Microsoft furnishes with Vista. Comodo is really a heavy duty product, and it is free, and seems to work great. I have never had any viruses on my computer using Zone Alarm and AVG, and that is continuing with AVG 8.5 and Comodo. I have Comodo and AVG 8.5 on both of my Vista comptuers, and one is 32 bit and the other 64 bit.