Aperture video not working

Hi all, I have Aperture running on my MacMini...but for some reason for the last 6 months, the video has stopped working. I am running v3.12 on OSX 10.6.7

Error description: thumbnail for videos appear. When I try to play the video, I either get a red tint (S90 videos) or audio only with no visuals, but I do get the play/pause controls (5DII videos). The videos play fine in QT by the way.

What I have tried

-repairing library and library permissions.

-using referenced and managed files.

-rebuilding library

-exporting library and re-importing into a fresh library.

The last stepped got the video working for a few hours...then it went back to how it was before.

When I load the videos into Aperture on another computer, everything is fine.

I am stumped. Any ideas out there? I REALLY dont want to uninstall/reinstall....I have a lot of plugins to re-download...