Quicktime abruptly stops recording video

I've tried to record videos with my webcam using QuickTime. I had previously had no problem, getting videos up to an hour long, no problem. Now, it randomly cuts out around 15-20 minutes, with the following error:

And I don't know what else I can try!! The screen recording worked fine, it's just the movie recording. This happened while I was on OS X 10.10.4, and now that I have updated to 10.10.5 hoping the problem would be fixed, it's still happening. Any ideas on how to fix it?