I read the original post and I think my problems are the same; about a month ago, I was watching a YouTube video on 3G and the phone froze completely. I had to pull the battery. Since then, under heavy use, my HTC Incredible has been rebooting, sometimes in a cycle until I pull the battery. Most noticeably, it happens watching YouTube videos, cycling quickly through photos on the Facebook website, playing Angry Birds for more than 6 minutes or similar heavy use.
I don't remember when the full version of Angry Birds was released, but things I've read and experienced seem to point to that as a culprit.
I was on stock, but since I didn't feel like going into a Verizon store (their solution to my horrible battery life: run an App Killer..derp) I thought I'd try rooting and flashing a new ROM in case it was software. SkyRaider and MIUI have both faced similar issues, though not to the extent stock did. In stock's defense, I used the latter two much less; only a week each so far. Also, with setting up my new system, I didn't have much time for Angry Birds. The first time i played for more than a few minutes was today and this was also the first time MIUI rebooted.
Is this just an overused CPU/overheating battery issue? Seems to defeat the purpose of a multi-tasking smartphone..