Keyboard/Mouse Freezes

[tumed]

My built-in keyboard and ultranav mouse freeze pretty frequently. I can be in the middle of typing a word document and the keyboard will stop working. The only way to get it to work again is to put the system to sleep for a few seconds, and about 50% of the time when it wakes up, the keyboard works again. I can also reboot and the keyboard starts to work again. I have not figured out what the timing of this event is. I can type a few words and it might freeze, or I might be able to type several paragraphs. The keys that are not affected are the function keys. Please help!
Thanks.