SOLUTION
Ok, I had This issue only two weeks ago. No matter what ROM I flashed to, Stock, Custom, Etc, nothing would work. I have the fix here, and this will get you going for sure. The only way this will not work is if it's actually a harware issue, and your device is pretty much screwed if so. Don't ask why these particular steps work to resolve the issue, becuase I have not one single idea. However, this will work. You have to follow EVERY SINGLE STEP, IN THE EXACT ORDER, or you will not get it going. Anyway, I hope this helps.
*Do a HARD RESET on whatever ROM you currently have on your device (Manual Hard Reset)
*Once the Device has finished the Hard Reset Process, you will come to the Configuration Screen which will say "Tap Screen To Continue" (or something close to that).
*DO NOT TAP THE SCREEN!!!! Leave the device on that screen. Do not proceed any further what so ever. Do not go to the screen calibration, auto run, etc. If you do go past this screen, turn around and do another Hard Reset.
*Conect your device to the PC. (While still on the "Tap To Continue" Screen). On most ROM's, you should still be able to connect to Active Synce, eventhough your still on the first screen. IF YOU DO NOT CONNECT TO ACTIVE SYNCE its fine. Simply enter "Bootloader Mode" manually. It doesn't really matter which way (I suggest active synce if possible), as long as you do not go past the "Tap To Continue" Screen!!!!
*Flash your Original Stock (shipped) ROM. Do not use any type of modified version of your original ROM, Do not flash to any custom ROM from here. Flash ONLY to the exact shipped ROM for your device/carrier.
*Once you have finished with that, pull out the batter before the device starts up. Leave it out for about 10 seconds, then put it back in.
*When the device powers on, you will come back to the "Tap To Continue" screen again as always, on almost every ROM i've ever seen. DO NOT GO PAST THIS SCREEN!!!!
*From that screen, do a Manual Hard Reset. This time, once it's done, go ahead and go thru with the complete setup. Let auto config run, screen calibration, etc.
*Now, after the device does it's auto restart, it will power on, now, DO ONE LAST HARD RESET! Before you mess around with anything on it, do another hard reset.
*Your Done!!!! Go ahead and set it up, and you will be good to go. Should be anyway. I've directed a few ppl to do this, and never had any complaints yet. You will be able to flash any custom ROM's now as well.
Again, I have no idea , not one clue, why this works. However, it does. I had tried everything in the world to get mine going, but nothing. And I'm telling you, if you do not do everything, every last reset, every last hard reset, this won't help. When you get to the very last hard reset, it may be optional though. In my experience, if you go without the last hard reset, your device will work fine while you stay with that stock ROM. But without doing it, you will have the same problems when you flash to another custom rom again. It's that way for anyone I've talked to for some reason.
But Hope this helps!!