Genocidicbunny
Bug squasher
You leave Firefox running for that whole week or do you close it when you're done?
If the former, Firefox is simply running up its memory usage. That behavior's largely neutered in Firefox 3, but that's still in beta.
Then I guess that behavior is largely based on your computer and your specific setup as I have, at the moment at least, been running firefox constantly for over 3 weeks ( Thats without closing it once) and its still running fine.