Quartz Screensaver with Video - synchronous not fluent, asynchronous crashes

hey, I'm building a simple screensaver with video in Quartz Composer. Basically it's a Movie Importer patch connected to a Billboard. The movie is MPEG-4 encoded. When I set the patch to 'synchronous' mode, I get very low FPS (drops down to 2!!) - the movie doesn't play fluent at all. Changing the video patch to asynchronous mode seem to do the trick - Test & Preview mode work perfect. But now the problem is, that the actual Screensaver keeps crashing asap the video starts... :( Any idea how to get fluent output in synchronous mode or to ensure asynchronous mode keeps the screensaver running?? Cheers!