Okay, that looks wrong. Do you have several dozen Flash applets open inside Firefox? I'm guessing no.

Seems to me something has gone haywire with the Flash plugin. Just to be sure, you could try disabling it and see if that prevents the problem. Tools->Add-ons->Plugins->Shockwave Flash->Disable.

Assuming it is the problem, though, I'm not sure how to resolve it while still leaving Flash active. Let's test first, huh?