Hello, i have an old Pc chips a33g motherboard that will not post if i plug in a regular ps/2 keyboard thus making the thing useless. Normal operation resumes if i turn the computer off and disconnect the keyboard.
You should try a usb keyboard, or check the backplate for intrusions. Those backplates have leftover metal tangs that have to be bent out of the way. Check for a grounding or short issue. You can also remove the board and check around and under it for metal objects touching the board.