Since I've been using Firefox on my 64-bit Windows machine, every few minutes the browser stops responding, with "Not Responding" in the title bar and the screen fades out for a few seconds. I've Googled this issue and it appears other users are experiencing this too, with some suggestions that it's caused by the Flash plugin. I don't want to disable Flash, 'cause I like to watch videos so can somebody tell me if there's another way to solve this issue?
Assuming that you're using the latest version of Firefox (3.6.x), it splits Flash (and other plugins) into a separate process called "plugin-container.exe" that you can see in Task Manager separately from the main firefox.exe process, do you see that using a lot of resources when your Firefox freezes?
If not, then this may not directly be Flash freezing the browser.
(On another note, I have Flash and 32-bit Firefox running happily on 64-bit Windows 7 Enterprise and don't see these freezes)
Update in 2014
These days Mozilla have some knowledgebase pages on troubleshooting problems with the Flash plugin Adobe Flash plugin has crashed - Prevent it from happening again | Flash video won't play full screen on YouTube, Facebook and other websites. Though what fixed recent Flash not responding problems for me with Flash 13 on Windows 7 was Disabling Protected Mode in Flash 11.3.
The last resort option (that I followed) in Adobe's FAQ How do I troubleshoot Flash Player's protected mode for Firefox? is:
Yes there is. Adobe has got a special website about this problem. You will need to install and use a 32-bit browser to resolve this problem.