Odd Keyboard/mouse failure after waking from sleep

Question

Here's an odd problem that's been bugging me for awhile now.
Occasionally my iMac will not allow me to log in after waking from sleep. I always log out of the machine when I'm not using it, and after a bit it goes to sleep (usually I'll just click the "sleep" button on the login display).
It wakes up with a wiggle of the mouse (Wacom Graphire), a tap of the keyboard (recent wired but numeric-keypadless Apple) or if I hit the button on my Griffin Power Mate.
But then I cannot do anything. If I click any of the edit boxes in the login window, or any of the buttons, the mouse jumps to the "sleep" button but does not click it. I can't enter a username or password because those edit boxes never get focus.
The machine is otherwise alive, as I can ssh to it from another computer or my iPhone and then from the command-line do a
$ sudo /sbin/shutdown -r now
for an orderly reboot.
Very bizarre and rather annoying ... this has persisted since I installed Snow Leopard. Clues, anyone?

Answer 1

Some, but not all of the time that the tower goes to sleep, when it wakes up the mouse works, but the keyboard does not. A restart solves the problem, but that's not practical.
My aluminum keyboard did exactly the same thing when used with the USB extension cable, but not when plugged directly to the computer. Usually, unplugging the keyboard for a few seconds would fix it. The Apple store replaced the keyboard, and I have had no problems with the new keyboard.