Htc vivid will not stay on

Power it on, i think its about to start after AT&T screen but all it does is "Android is upgrading 0-87" after that starting application... phone pops on for 3 seconds and after it says "starting htc sense" the phone turns itself off then start the process again. I've done the htcdev thing and nothing seems to work.. how can i wipe my phone clean or put it in USB debugging mode if i cant keep the screen on. Can someone please help me.. I've spent my entire weekend trying different things but nothing works.