It just happened to me a few minutes ago. My empeg has been running all day - about 12 hours. Lots of reboots, http list transfers, loads of SITE RW and RO and small FTP transfers.
The first time it happened I wasn't using Hijack, so it isn't the cause of the problem. I've been running Beta7 since it was released, but I can't recall if the first time was with Beta3. It has never happened in the car yet. I use the player at least 2 hours per day in the car - 1 hour in the morning and 1 hour in the evening.
Bruno