Keyboard is unresponsive in WideScreen Games!!

Hmm.. someone help me out here please..

basically i bought a new wide-screen monitor (http://www.scan.co.uk/Products/ProductInfo.asp?WebProductID=434443), and when I play any games full screen at any resolution including the native res. (even in standard aspect ratios and widescreen ratios), the keyboard becomes extremely unresponsive. i have tried turning the settings down aswell but it still doesnt work.

i changed the setting in CS:S to run game in window, and i can play it at any resolution (upto my native res obv.) without any problems. but then i have the ugly border and id much rather play full screen.

PC Stats
Intel P4 3.2 Ghz w/ HT
512mb + 256mb DDR 400 Corsair Value Select RAM
LeadTek Nvidia GeForce 7600 GT
19" Iiyama PLE1900WS-B Monitor
200gb Sata hdd (cant remember the make atm)
500w Akasa PSU
anything i missed out? (lol i need to upgrade soon tbh, this rig is getting quite old now i think of it.)

Sounds like a software problem. Have you tried the same setup with a different monitor?

If that doesn't do it, then how about removing anything that interacts with your monitor like: monitor drivers, monitor software that you might have installed, refresh rate fixes, etc....