This is hard to describe... When I capture longer clips, the last ~1/3 of the clip will not play captured video all the way through. It reverts back to the captured picture head and plays that picture instead. When I put the Overlays on and add TC Overlay then I can click on the correct new captured footage, and I can click frame by frame through the right picture, but as soon as I hit play it reverts back to the wrong, repeated footage. The audio however is all original, "correct" and unrepeated. I can even edit the correct source footage into the timeline and play it no problem, but in the Viewer window this problem remains. I'm stumped...

Play the clip in QuickTime Player. Does it have the same problem? What Capture Scratch are you using -- something in your hardware could be corrupting your data or confusing the location of certain pieces of information.

Thanks Derek. When I play it in Quicktime it's fine. As far as I can tell, it's writing to the Scratch Disc OK - though right now, that's my favorite theory as to what's wrong - corrupt data. I can even recapture the corrupt segment going back to the source tape and have it play back fine in the Viewer - no problem. I think it might have s.th. to do with the fact that it's HD, and that when it screws up it cues back to a place where there was a previous TC break. But I'm still stumped...