It actually seems to work better when I convert the audio files to wav. I would prefer to be spared from this step, but at least it’s better than no audio at all (or wicked audio).
I have the exact same problem. With previews it’s okay if it doesn’t work perfectly (even if it’s annoying as h*ll), but the real problem is that even the renders get messed up. I also use 44khz 16 bit aiff, it has always worked for me before CS5.