Wireless keyboard prob!

Hi guys, i have a tsunmai wireless keyboard and mouse (usb). I cant get the mouse to work, but i aint too bothered about that. But the keyboard, when im playing games, and u hold onto a key, ie W, it stops working after about 5secs, u need to release the button then press it again. Ive tried replacing batteries and moving reciever but no luck. Anybody have any ideas…thx sasarchiver