I'm getting a similar issue but it's only on Cliffhanger, Fire & Ice and Titan (These use mp4 files, the others are using m2v)
The video is playing ok, but the sound is stuttering.
I'm also using a Realtek onboard sound card, but I'm using 64 bit Ubuntu.
As with the other poster, if i play the mp4 file on it's own, it plays fine.
However, Timegal seems fine!