In the past I've used the Nanocosmos editor and the merge and cut feature in TMPGEnc to successfully edit video files. Just recently, however, a strange problem has come up. In both programs, whenever I use the slider bar below the preview window to move the video ahead to the point where I want to cut, the video will refuse to run after that except in two or three second spurts. The only way it will run smoothly is if I restart it from the beginning. If I then use the slider bar, the same thing happens. I thought maybe my hard drive needed to be defragmented, so I did that but it didn't help. Still have the problem.

Has anyone seen this problem before? Any idea what could be causing it?