I had this problem happen last night. I was using the internet when all of the sudden I had a force close storm. Literally every application I had running started to force close and wouldn't stop. I powered down the phone, and then got stuck in a reboot cycle. Mine was between the HTC quietly brilliant screen and Verizon Wireless black screen. After reading all of the tips here, I did a manual clear of my data, and it fixed it.
This resulted from a low space dilemma, as I have been posting about in that topic on this sub-forum...had been having that issue for about 2 weeks, and after talking with HTC and Verizon, I could not rectify the problem. So I guess this was like a crash on a computer? Not really sure, but the phone seems to be working fine after reset...anyone else ever remedy any of these problems without a reboot?