Gave 544 a try with four 25 min OTA HDTV (720p) segments - Opened them, edited them, saved them as .ts files, and then added them to DVD title list to create DVD. Started the process and about 30 mins. later got the message (title of thread), with option to recover process after restarting VTS.
Thought they might be somehow bent, so tried to create separate dvd files of each. That worked, but VTS couldn't open them, saying it couldn't "read a .vob file" or couldn't "read a .ifo file." (logfile ftp'd - I hope)