Same thing happened to me. I built a video recently using 7.11; I upgraded to 8.23 and decided to make some additions to the video. When I attempted to insert the new sequence into the overall video and replay an exception occurred. I've tried downloading the latest code (8.28 - which is beta by the way) and pieces of the video started disappearing. I uninstalled 8.28 and reinstalled 8.23. At this time when I load the project videopad simply hangs on "processing" the audio files. Interestingly, other nchsoftware applications can read and process the audio files just fine. Videopad is hitting the disk hard when it is stuck in processing audio - (20 MB/s and 29% of cpu cycles). It is as if there is some threads fighting for a semaphore file hidden on the disk somewhere that the program is waiting to clear somehow creating a livelock situation. I might try reverting to the 7.11 version to see if that will clear it up.