I ordered the replacement digitizer and replaced it according to the instructions (from HTC Vivid Screen Repair Guide
). After I put it all back together, I held the power button down and nothing appeared on the screen. Oddly enough, all the phone does is vibrate every 9 or 10 seconds. It will only stop vibrating if I remove the battery. When I put the battery back in, it will only start vibrating if I try to turn it on or I plug it in. I feel like the repeated vibrating is a diagnostic code of some sort, but I can't find anything online.
The phone was working prior to replacing the digitizer.
I've contacted RepairsUniverse to see what they say, and am waiting to hear back. I've also called HTC Out Of Warranty Repairs for AT&T (1-888-354-2375) and have a ticket open with them. I'll soon be sending my phone to HTC, but if there's something easy I can do myself, I'd rather do that.