Comment 94 for bug 104470

Bug 177856 refers to flash crashing, leaving a gray or (invisible) white rectangle where the flash content (i.e. movie) should be. Firefox does not crash in that bug. It also only exists on 64-bit SMP (multiprocessor/multicore) systems. This bug (bug 104470) is not the correct bug report for your issue.

Are there any specific symptoms which are different in your case?

As a side note, I myself have not yet upgraded to Firefox Beta 5, so I will wait upgrade other packages first, and see if the problem reappears. Thanks for the heads up.