I'm using Avid 7 on my Imac 2.9 Intel core i5 / 8 GB.
What seems to happen on a regular basis is a color shit and / or a weird jump on video clips under text layers / or lower third layers after export. Inside AVID everything looks correct, it tends to happen when I export the QT movie. I tried rending the videos (all layers) and it still does this. Sometimes the solution is I have to remove the text layer and render it and then put back the text layer and it will solve it. Other times, this doesn't work.
I'm not sure if it would help but try doing a video mixdown of the layers first?
I know when I use text over colours they fade at different times when using a quick effect so it may be the same sort of issues with colour.