Firefox Freezes

Lately I've been having some problems with Firefox freezing. I'm using release 3.0.11 on Mac OS X and sometimes when I go into Gmail or even Twitter, I cannot push buttons. It doesn't seem to happen when I first start Firefox, but after I've been running it for a little bit. I just wonder if anyone else has had any similar issues with Firefox occasionally freezing on them. The way I solve the issue is simply by restarting Firefox when this happens, so it does seem to be some sort of cache/memory issue. I haven't been convinced to switch completely away from Firefox but I have been using Safari more and more.