Using XP, Word 2003, and a Logitech PS2 keyboard.

I am typing and without rhyme or reason I lose keyboard function for appx 30 seconds. I have mouse functions, but cannot type anything. The first time it occurred, a day ago, I clicked keys, moved the pointer, clicked several keys, etc. It happened again, maybe 15 minutes later. The third time it happened, I waited a minute and the keyboard resumed functioning. Now, when it happens, I wait 20-30 seconds and the keyboard functions return. I have been using this keyboard and this computer, without any significant changes, for the past several years.

What in the heck is going on and how do I prevent this from happening?