I have a possible similar problem with my canon mv6i mc. When I play back my recording, the image breaks up into blocks, flickers and becomes distorted, no sound though. Yet at other times it records fine. I have used a tape cleaner, but the problem can re-occur. It might be that we both have a problem with the CCD's image sensor in which case if you contact Canon they will repair for free even if the warranty has expired, check for nearest repair center by going to canon's homepage. http://www.canon.co.uk/ I'm going to send mine away as I am getting fed up with it working and then not working. Hope this helps.
Rich
May 2006