Try this. It could possibly be – depending on your PC specs – that the video recording is taking up too many system resources. I'm not sure about your PC specifications so this is just a suggestion to get started.
Ctrl-Alt-Delete and bring up the Task Manager. See what the CPU / memory usage is at the bottom of the window. If this is in the high 80's to 90's it may be causing the recording to fail. Try turning off all running programs and anything running in the system tray in the bottom right hand corner.
Is there a video recording quality setting in the software at all? I know AMCap is fairly basic so you might want to try something a bit better that has some kind of caching built into it so your disk has time to catch up – if that is the reason it is failing.
If the software has a video quality setting, try setting this to its lowest resolution / MB per second settings.