Hanging problem with Firefox, Thunderbird, and Internet Explorer

[NorCalDave]

I'm having a problem with Firefox, Thunderbird, and Internet Explorer hanging. I built my system a little over a year ago and am running XP with SP2. Initially, everything worked fine - the hanging problem seems to have started sometime in the last 4-6 months.

Symptoms

While using any of the above mentioned applications, I get frequent instances of hanging lasting 15-20 seconds when I launch the applications, open a new Browser window or tab, click a button to initiate a action, refresh a page, check for new mail, etc.

I'm running Comodo Firewall 3.0.20.320 and also Comodo AntiVirus Beta. Have posted on the forums there but figured I'd post here too in hope of finding a solution.