No funtion the X key in Mac OS Snow Leopard 10.6.8

Hi guys, I have a problem, the X key in my keyboard no funtion, it´s no the keyboard, because I've tried it on both mac keyboard that I have, the only way that funtion is reboot the OS, but just only few seconds, after that, the X key stops working as if by magic, in any of the programs I have.

My gear: Mac mini late 2009, 2,26 GHz, 4 GHz Ram, Snow Leopard 10.6.8

Thanks a lot.