I'm having the same problem. It just started tonight, and I found this thread (and forum) searching for a fix. The DI (with 2.2) will get Past the first white screen, past the HTC logo, and give the animated red splash screens where it audibly says "DROID". Then after awhile it just reverts to the HTC logo and starts again.
I suppose I'll take it to Verizon tomorrow (If I can get out in the snow..not looking good) and give them CDS's solution to try out if they find no other fault, maybe ask for them to try a different battery.