I plugged in a USB drive when the computer was on. I got a "USB device not recognized" error and right afterwards, my computer froze. I could not even hard reset it. I held down the power switch for 30 seconds and nothing happened so I had to switch off the PSU. From then on in order for the computer to POST at all I needed to switch off the PSU and remove the CMOS battery. Even though I managed to get the computer to POST by removing the CMOS battery, I get a "USB device over current status detected shutting off in 15 seconds" error message every time I got it to POST.
I cannot enter the BIOS either, but I did manage to get into EZ Flash 2, but only with a PS2 keyboard. The computer stopped detecting the USB keyboard.