The HDMI port can get disabled by shining a flashlight on the back of the Tv near the HDMI port. It's a "feature" thought up by JVC to prevent someone from running the Tv while it's open (exposed to light).
I've had to perform the reset procedure 3 and 4 times sometimes to make it "stick".
Yes, it can be reset successfully and still have a defective board. The only fix then is to replace the board. Here is the part you need: http://www.encompassparts.com/products/?SRP0D045A-M2-R The installation is very difficult. If you fudge a connector, you are screwed:
Remove lamp door.
Remove rear cover.
Remove metal cover where the inputs are.
Remove screws, unplug some connectors, and slide the entire chasis out.
Disconnect several connectors to the Digital board.
Remove one screw holding board in and take out board.
Separate board from daughter board/bracket.
Install new board and re-assemble.
After Tv is completely re-assembled, plug in and power on.
Perform the HDMI reset procedure.
Do not shine a flashlight near the back of the Tv.
Do not put the back of the Tv near a big open window where light can shine in on it during the day.
Test HDMI port.
I wish you good luck (no joke)!