Another white preview screen thread

just purchased AE CS4, installed mocha and have found a problem
ive read other threads on here with the same problem but ive tried all the ideas listed and im at a loss…
i try uploading any file format that opens in quicktime and get a white preview screen
my graphics drivers are up to date, i have the latest quicktime version (installed it and tried mocha again before posting), i have mocha v1.2.3 soho ed, I’m running Win 7 32bit
so far ive tried:
opening in xp compatability… nothing,
converting file to quicktime format… nothing
updating everything i can think off inc quicktime… nothing
dont know what else to do…

It’s probably the codec on your quicktime. If you render out a sequence of frames that will always be a workaround you can use.