The random reboots have been happening to me, as well... and I am about to throw my phone into the fireplace. I have owned it since September and never had a problem until the 2.3.340 update. Not only the random reboots but the gallery not working correctly and me having to use another app to view my images.
I've about had it, really.
I know that my reboots are definitely tied to the freezing of apps through Titanium Backup. I froze all the bloatware. Immediately afterwards, the phone started rebooting at least 2 to 3 times a day. I unfroze everything and it went a week with 0 problems. Froze apps again. Reboots a couple times a day. Now I am in the process of freezing one app every couple days and trying to find out which one is causing the problem.
I've had about 1 spontaneous reboot per day since the update occurred. Before the update, I never had any reboots.
BTW...I'm rooted, using Titanium backup and I have a small number of apps frozen.....hmmmmm.......