Breaking sleep mode

When the machine goes into standby mode the only way I can get it out of standby is to unplug the keyboard and plug it back in again.
Frank Pittel wrote on :

My new (well not so new anymore) mac mini has recently come up with a new problem. When the machine goes into standby mode the only way I can get it out of standby is to unplug the keyboard and plug it back in again.

This all started after I installed my Epson-2200 via usb. Thinking that it may be related I unplugged the keyboard. The only thing I have plugged into the usb ports is a keyboard and mouse. Anyone have any idea on what I may have done wrong and more importantly how to fix it??