I have noticed the same problem with targa sequences. my comp only included image sequences, and shapes and text building directly in After Effects. I tried rendering a full HD comp in 32 bit, with a targa sequence. i am using a lot of vignettes with the ramp scatter, therefore im trying to avoid as much banding as possible. the first 50-60 frames were okay, then everything came out tinted blue. im using CS5.5, if restarting the computer seems to do the trick, hopefully CS6 might not have this problem.