I would keep the battery out for more than 10 seconds after pulling it. Electronics doesn't discharge instantly.
However, none of the changes you mention should be a cause in itself. Bad cards can cause odd problems, but why should that correlate with plugging in? You could have a software condition that is triggered by plugging in, but a factory reset didn't fix it which makes that less likely. So my suspicion is that it might be hardware. Did it start abruptly, you do anything in the day or so before?
I guess that if nobody has any other ideas you could run the 2.3 RUU again and see whether the problem is still there. If it is that only leaves hardware. Do check there is nothing stupid like something in the charging socket.
When you say freezes, just to be sure, you mean that it does not respond to the volume or power keys (the touchscreen doesn't work in hboot/fastboot), and the word "fastboot" does not change to "fastboot usb" when connected? If so I think it must be hardware, as a software problem with the android OS would not affect the bootloader.
I know that in my region the warranty is 2 years, so only the early adopters are outside the warranty period.
Yes, the buttons does not respond in fastboot after plugged in usb.
I tried again to run RUU this morning, it was ok at first (not hanging), but it works only halfway. now it wont load up and stuck at HTC page. Unable to run the RUU on fastboot mode coz no driver for it.
Can any1 help to point the driver? tried on the xda but no luck installing.