I've seen that happen with VLC and an unsupported file format a few times when it first came out. Trying to stream without enough bandwidth (Like 1080P HD over WiFi), or to play files with too high a bit rate for the storage's bandwidth can also cause this. Video from a cheap and slow SDcard will also cause this.
Typically, you go back Home, then /Settings/Apps/ and use the clear cache and force stop functions and your good. upon re-starting the software player, pause/stop ASAP, then switch to folder view or file selection gallery before the system freezes over. In one instance, I had a corrupted file which forced me to un-install my player and reinstall it.