Comment 17 for bug 66350

I have this problem as well using Ubuntu 8.04 and the latest patches of everything. The only thing unique about my system is that I'm running a custom Hardy kernel to support PAE and Xeon processor.
Typically I can kill the firefox process and bring up a new window, but that is always a pain.
I can also reproduce this at will by trying to open three separate Firefox instances. I can open two, but when I try to open the third, the first two go to gray screen and firefox is using 100% of CPU.