Several times since yesterday, I can't close the Firefox 3.6 browser. I have to go to task manager and kill the task. I don't have any such problems with IE or chrome. Anyone knows how to fix this? I have tried rebooting my computer but that did not help.

Several times, my browser just freezes and I can't close it. I have to start the task manager and kill the task. After that I am able to restart firefox. After visiting a few web sites it freezes again and I have to kill the task again. I don't have any such problem with IE or chrome. Does anyone have a solution? I have tried rebooting my computer but that does not help. This started happening 2-3 days ago.