Here is my setup:

MacBook Pro 17" (Early 2008)
OSX Lion 10.7.2
2.6 GHz Intel Core 2 Duo
8GB RAM
NIVIDIA GeForce 8600M GT 512 MB

Serato Setup:
Version 2.3.0
Using MixEmergency for video
USB Buffer is at 2

I keep all my videos on a external HD.

When I am playing music, and load a video sometimes is works and fine I have no problem. But sometimes when I lad a video it either takes a while because the mouse timer comes on. Then when I play the video, the wave forms have gaps in them and the song will not load all the way. Also there are times when I am playing videos an the wave forms start shaking and lagging. I wanted to know if there are particular setting that I have to adjust, or is there something wrong with my computer.

Any help with this would be great. Thank you in advance.