I have EXACTLY the same problem.
It happens when transcoding AVI files (XVID and DIVX) and possibly others.
Nero Vision begins working and terminates after a random interval.
No other applications are affected.
When minimized to the tray it can terminate and still stay in the tray until the mouse passes over it, when it just vanishes.
It is NOT running in TaskManager.
Nero Vision is a real resource hog and often wants over 90% of my CPU despite the settings chosen.
It terminates as soon as another program grabs some CPU and keeps it for longer than Nero Vision decides it has had enough.
I have over 100G free on a 1T Drive and oodles of free RAM.
I’m running Win XP with all the latest updates, Roger’s Online Protection for AV and Firewall and Ad-ware for spyware.
Mostly I use FireFox but it happens without being online and also when only IE is running.