I've experienced this glitch twice now, and the only way to fix it is to reinstall videopad. After making several edits to a video sometimes the file gets frozen on a single frame while buffering. the audio is fine, but the video never goes back to normal. It usually happens right after an edit. I'll include a screenshot that shows my video stuck on a single frame for nearly 20 minutes (entire remainder of the video file) the file in question has no playback errors at all.
https://drive.google.com/file/d/0B2vdKjMiYJgdU0VpVnpJOVlZeVU/view?usp=sharing