Keyboard light isn't on when I start up

Hello,
My keyboard is 3 years old and is working perfectly fine. These past few days when I've been turning on my computer the green keyboard light doesn't turn on anymore. My screen says: "Check Signal cable" and everything is plugged in properly. I've tried everything I know to fix it but the last option I want to do is get a computer expert or buy a new keyboard. My keyboard worked somehow last night after over 9 hours when I returned to it.
Now it isn't working again...Any idea of what I should do or just buy a new one? If you need anymore information just ask me and I am not a computer expert so please try to keep it simple.

Some Details
Keyboard name - Cisnet
Type of computer(I think) - Windows xp professional home edition '07
I use Mozilla Firefox