Movie: poster and audio, but no video

am running Windows XP and Acrobat 8 Pro, InDesign CS4. I tried placing the video into ID and then exporting with the video already in the PDF. The poster shows and the audio plays, but the what should be video just turns into a grey box. However, I can play the movie fine right in Quicktime. Both the movie and the PDF are right on my desktop, to avoid any server latency issues. Am I doing something wrong, or is this a software bug? Why doe my movie work fine in a player but not in a PDF?