Okay, since a powered HDTV antenna will inject DC into the cabling and can cause the Mainboard to lockup or glitch- again, I need to know WHAT specifically you're running for:
1) An HDTV antenna.
2) An amplifier/splitter/booster.
3) What have you replaced so far and HAVE you tried another antenna with the same results?
A really good test, is to take a cheap, brand new HDTV antenna and LOCALLY connect it right to the TV and see if the issue persists. If it does NOT- then you have excess DC entering the coaxial cable.
If it also does- then you have received a faulty replacement mainboard.
As a workaround, instead of buying mainboard after mainboard- consider an external DTV tuner box for around $35 and simply connect it to the TV's AV jacks and bypass the TV tuner altogether.
Anyhow, please check the above as it is all very important steps in troubleshooting, then let me know what you find.
If you need further assistance let me know. Please do not forget to click the 5 STAR RATING, at the top of the page for my efforts. It is my livelihood and you can follow up at any time if needed.