keyboard error 2 different motherboards

I have a 6 month old system that i recently got a keboard or no keyboard error present on. Actually I was working in a DOS program, it locked, and then on reboot got the message. After changing keyboards, it still did not work. I changed the motherboard and it worked fine. 5 days later the same thing happenned. I had an extension on the keyboard originally, took it off and it worked fine for 2 days. Now it’s at it again and I feel there is no way it can coincidentally be a brand new motherboardagain! Any ideas would be greatly apreciated.