Video and Audio problems

I'm currently running Snow Leopard, and haven't had any issues until some weird stuff started happening this evening. Just wondered if anyone recognised the issue.

I was playing Youtube videos, all was grand. When I went to play another one the picture was jumpy, as if it was playing it too fast. There was also no audio. I thought it might be an issue with Youtube. I checked a different streaming video site and had the same problem. So I thought it might be my connection. I opened VLC and played a video from my HD. The picture was fine, but again no audio. So I opened iTunes and tried to play a song. The play button turned into the pause button but the song wouldn't play.

I checked for software updates and installed them. When it rebooted it made a strange noise. Then it displayed the normal white startup screen only this time it had a progress bar. Once this was done it restarted again and made another weird noise. It then started up seemingly fine.

Fine people of Boards. WTF?

EDIT: Looks like the noise and progress bar might have been caused by the software update. I just checked the log and the firmware was updated. Still not sure if thats the actual answer or not. Or why the video and audio went funny.