First, a little background.

I'm running a Kubuntu system with Compiz Fusion and firefox version 3.0.3. But I've had the crashes and freezes with earliear versions of firefox.

The problem goes like this. Essentially, Firefox would crash whenever two windows are open and then it is attempted to open a third window.

The third window would cause firefox to crash and it doesn't matter if the third window opens from a popup or if a link is opened in a new window manually.

I've gone through so many threads at the Ubuntu forums, many of which said Compiz-fusion, Java, and many amateur made extensions were the cause of firefox freezing on multiple windows.

Until today, I never would have guessed that the cause of firefox not being able to handle more than two windows would be the Google Toolbar.

So after months of searching for the reason why Firefox crashes on Ubuntu when it is attempted to open more than two windows the solution for my system was to uninstall the Google Toolbar.

So you might want to give this a try if you've looked into every possible reason for Firefox crashing when more than two windows are opened. Go ahead and give a try and remove the Google Toolbar.