it times happend to me too, not sure it's flash itself, i think it is from the plugin container from firefox if u want to try if its the problem, u can disable the plugin container by going in about:config in ur firefox and search for "dom.ipc.plugins.enabled", then put everything found from "true" to "false" then restart firefox if it didnt resolved your problem, just put back the previous values ps: plugin container was made to prevent crashing the whole firefox if only a plugin crash, so disabling it will disable this feature
Your problem has nothing to do with Windows 7, and everything to do with the fact that you're using a beta Firefox release. It's most likely a problem with the GPU hardware acceleration (which you can disable in Firefox's options), and I've seen the same problem with some Flash videos too. Also make sure to update to the latest version of Firefox (4.0b6).
I have the latest version. I think I've tested it on the stable firefox release (3.X) too and I had the same problem. I won't bother testing it again to make sure, I'll just wait for the beta release to become stable. Thanks for your help though
Firefox isn't (easily) available in 64-bit form for Windows, so the 64-bit Flash plugin isn't much use... yet.