Why do YouTube videos lag while audio is fine when I switch to 720p?

[Grounderz]

Hi guys,

I'm extremely annoyed by the fact that everytime I watch a YouTube video and switch the quality from a standard 480p to a 720p or 1080p HD, the video gets lagged out. The audio is fine on 1080p as it continues to play till the end without anything hindering it, but the video itself gets lagged out so this led me to assume that there isn't any problem with the internet connection. The audio is completely fine but the video isn't.

After restarting my Macbook Pro, everything returns to normal. In a short while when I try to view it in 720p again, it gets laggy again. I have no problems viewing it in 320p or 480p. I notice this happens after I installed a number of updates on my Mac OS X 10.

Here's a list of updates I made.

(1) iTunes 10.4
(2) Mac OS X Update 10.6.8
(3) iMovie 9.0.4
(4) Remote Desktop Client Update 3.5.1
(5) Digital Camera Raw Compatibility Update 3.7
(6) Java for Mac OS X 10.6 Update 5 1.0
(7) AirPort Utility 5.5.3
(8) Migration Assistant Update for Mac OS X 1.0
(9) Safari 5.1
(10) iDVD 7.1.2
(11) ProApps QuickTime codecs 1.0

Does anybody have any idea which of these updates that has caused my Macbook Pro to react unusually? Everything seems pretty normal except this YouTube video. For now, I just restarted my Macbook Pro and everything returns normal. I suppose it will happen again soon.

[Daforce]

what system do you have because maybe that is your problem