This was happening to me a few weeks ago then stopped. After a month or so of not happening it has started again. The phone seems to reboot itself around once per day. I only notice it because of the lovely loud boot sound. I've also noticed it seems to be at the same time as an email arrives. It used to be accompanied by a load of K9 email errors. These and the reboots stopped when I re-entered all the account settings, I may have updated the app at the same time. I've got 2 gmail accounts set up on IMAP, 1 POP3 Hotmail account (but now forwarded to gmail so get nothing through this) and 1 NTL account which I poll once every 24 hours. The reboot seems to happen when I get a gmail but usually just the first of the day. Anyone got a clue??