Grey firefox window?

[Mashy]

Installed Hardy this morning, and am loving it. I am however having one slightly annoying problem. When I am browsing in firefox, every now and then everything goes grey (within firefox) and I cannot interact with it. Everything else in ubuntu is fine, I can still do things, just firefox will not work while it's grey. It goes away after a few minutes though.

Any ideas what's wrong, and how to fix it?
Thanks.

[Archimedes0212]

this happens to me sometimes too. What I have done is added the "Force Quit" app to one of my panels. When Firefox dims out and doesn't respond I Force Quit it and then when I click firefox again it prompts me to start new session or restore old one. I restore old and everything is back to normal.