Ok here are some things to try.
like I said earlier I would turn of hibernation and try another keyboard or use a USB to PS/2 adapter and try that keyboard on the PS/2 port and see what happens
So to clarify, the USB mouse wakes the computer up, and you have full mouse functionality but the keyboard inputs are ignored?
Replaced the battery lately?
Is it a wireless keyboard you said USB and I assume it's wired
Give us as much info as possible your not giving us a lot to work with
Yes, the mouse is USB and never has a problem.
Lets not overlook the easy stuff. Have an old keyboard that you can try. So at least we know is it the software or the keyboard. Try replacing any drivers that are outdated.. Check it out in device manager.
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