My wife's myTouch 4g started locking up after I rooted it. I unrooted it, but the problem continued. I tried to do a factory restore and it would just boot in a loop ('my' screen only).
I discovered that I didn't have the stock ROM on the SD Card, so I downloaded PD15IMG then tried again. After several minutes, I came back to a blank screen. Now, the phone will not boot up into any mode, including HBOOT.
Is there anything else I can try before I call T-Mobile to see about a replacement?