So you've captured the video to the hard drive, and it starts jumping after a minute.
Never had a problem like that myself and i use a similar camera, sorry this is an obvious question but have you checked the tape in case it's chewed?
I think everyone with usefull advice from the UK is asleep, I'll do my best.
I think they would say:
could you give some details about what software you used to capture, what format you captured in and the pc setup you're using.
make sure the drive your capturing to is de-fragmented, this solves a lot of problems with dropped frames and stuff.
Panasonic SD9, Panasonic NVGS-75, Canon MV600i