I have an extremely similar, but apparently not the same, problem. Basically, I have the same symptoms as you, only instead of the "2 second" thing, I can't seek at all. It just sends the time cursor back to where it froze. Also, it usually freezes just the video and Firefox remains fine unless i close the tab or navigate away from the page. Unlike the problem here, Internet Explorer is also affected, and I've tried all the fixes I've seen here, and none seem to work, though I may be doing them wrong.