Agreed, I would try reflashing. Is it actually staying on non-stop? If the answer is yes, somethings wrong and a new wipe/install usually fixes sht like that for me.
My guess is that the rom changed the sensitivity of the proximity sensor. I know it's possible to change the duration on the prox. sensor, if stock is 1.0 second, and the rom you're on is .25 seconds for the screen to turn on, it's possible that with the angle of the phone on your neck it JUST slips out of range for a split second, then comes back in, allowing the screen to quickly flash on if the duration is set really short compared to stock.
this is just my speculation. I had this problem with my X and was able to change the proximity sensor settings, but don't recall how and don't know how to do it on the TBolt. Maybe if you google it...