A couple of possibilities,
1. Corrupt disk sector or bad file. Defrag your hard disk, delete all temporary file snad try re-creating your movie.
2. Corrupt memory address. Not my field of excpertise but I am sure some of our techy friends will point you in the right direction to check and fix bad memory sectors.
COMPAQ something or other with 500Gb Boot Disk, 1Tb external Firewire Disk, 4Gb Memory and a super duper sound card, 19" TFT Monitor etc etc etc
Sony TRV33e : Sony TRV310e : Canon XM2
Sony Vegas Studio editions to v11
Remember, there is always more to learn than there is to teach.