draceena, I had to use the Task Manager 3 times on Saturday to close FF 4.0, initially I thought it had to do with an Ashampoo program (a free burning studio) that I had installed, but even after uninstalling it, the issue persisted.
After a full scan w/NOD32, all was clean, so I knew that it was a bug in FF 4.0.
So for the rest of the day, I bounced between using IE9 & Opera w/no problems. Then Sunday, FF ran OK. It's ran fine since then. Mozilla is notable for correcting bugs on the run, which isn't really a bad thing, as they're open source, and can patch things in a hurry, once the issue is isolated. Hence the rapid releases for the 3.6 versions (now at 3.6.16), two versions once released within a week's time, to repair a bug.
There are already mentions of FF 5 & 6 releases by years end, 6 may be pushing things, but 5 may happen.
All of the other major browsers have upcoming plans for new versions, Opera has a new Beta out already.
FF 4 is looking good, I expect it to continue it's climb in the charts. Thanks to MS for alienating it's loyal XP customers for not paying their Windows taxes recently (a new OS), half of the computing world won't even see IE9, or the recent version of Windows Live products, while FF's stock will continue to climb.
Many thanks to Mozilla, along with the ones at Opera, Google and even Apple for still acknowledging XP's still powerful user base. While it's a declining base, it's still a few hundred million strong, and it's users deserves a new browser too, as they're still supported for another 3 years.