Diamond Flickering Screen

I have this problem that has bothered me for months.

One day I woke up and the battery was unexpectedly drained.  I charged it up and try to use it again, then suddenly the screen start flickering non-stop.  I thought it is a software issue, so I soft-reset the device but doesn't work.

After doing some research, I found out that it's maybe due to unsupported SPL version.  So my next attempt was to connect the device to the computer so I can use RUU to flash it with something that works.  Another problem arises that the computer doesn't recognize that I have plugged in my phone (ActiveSync doesn't work).  Thinking it might be the cable or computer's fault, I tried 5 different USB cables and 3 different computers - nothing works.

Next I thought there might be something wrong with the OS, so I hard-reseted my device.  Nothing doing - screen still flickers at the time of bootup (when the words "HTC Diamond") first appears, and ActiveSync is still not functioning.  My next thought is that the USB port is somehow broke.  But regular charging and headphone functions fine.

I do not have a warranty and HTC said that they would charge $400 to get it fixed (lol).  I'm hoping an expert here could point me to a solution.  My diamond has been laying around lonely as I cannot use it for anything (hurts to look at constant flickering screen & battery drains in 10 mins b/c screen).

Thanks in advance