I have only shot 5 minutes of video with my HV20 all test clips. I played the tape in my HDR-HC3 to see where the gain was on all the video . I put the tape back in the HV20 and it will not play, I get a blue screen and the time code doesn't move but when I stop the time code jumps ahead to where it should be.

I put the tape into the HC3 again and it plays . I recorded new video after the 5 minute mark with the HV20 and it plays fine ,if I rewind into the original 5 minutes it will not play.

Is this a known thing or am I haveing a wierd situation?

Odd. Could you try repeating the circumstances again, and repeating the steps?

I've never had problems playing Sony HDV footage in my HV20, and I know my production partner has played Canon HDV footage in a Sony.

Try cleaning the head on the Canon, or both cameras for that matter?