Youtube skips back when maximised

As the title says when I load a video in youtube and maximise it to full screen, it jumps back a couple of seconds. Even when minimising full screen back to the original size it jumps back maybe 2 seconds. I am using Firefox 8.0, I have tried Chrome and IE with same results. When doing the same on my mac with the same two browsers it doesn't skip back. Anyone else having these problems ?
Thanks

Are you saying the playback is choppy or that it goes back in the video when you maximize/minimize? If the latter, that is normal.

Yeah it goes back in the video, ok though it was just me. I wonder why OS X doesn't do it ?