I'm a bit of newbie to digital cameras and forums. I have just bought an CANON SD800 (IXUS 850) and I am having trouble playing back videos on my PC. First of all, both video and audio were jumping/jerky playing back in Quicktime, Windows Media player and RealPlayer. I re-installed Quicktime from the CD that came with the camera and the video now plays back perfectly, HOWEVER the audio is terrible (worse than before). Any ideas please? I have tried various MJPEG codecs but none worked at all for Windows Media Player.

It's not likely that you're going to get an answer on the Canon forum. I think we're pretty much all still photographers. But we do have a video forum. I think they might be able to offer more help:

Digital Video Forum >> (http://forums.photographyreview.com/forumdisplay.php?f=28)

Good luck!