[American Constitutionalist]

It could also be something simple as a bad driver or corrupt driver for the USB hooked up the the keyboard.
Another thing about the PSU ( power supply unit ) when they go bad ? the computer acts really fully and can actually shut down by it's self.
It won't hurt even if you get a new PSU with a few more watts than the old one... most of the time, the manufactures put lame PSU units in computer that just barely supplies power to the computer.
100 extra watts won't hurt, and your computer only uses that wattage when it needs it, lets say ? a 500 watt PSU ? it's not going to continually run at 500 watts max all the time.... now ? if you have a heavy use of multi-bluray drives, 2 GPUs a 6 core CPU, then yes, that 500 will be used most of the time.

[American Constitutionalist]

Typo correction :

Another thing about the PSU ( power supply unit ) when they go bad ? the computer acts really funny and can actually shut down by it's self, or won't work at all.