I am sorry if this sounds stupid but... get a wired keyboard
Check if the charger is charged or if your batteries are "full". Also incase you have a signal reciever connected at your PC try to get it as close to your keyboard as you can, that's what I did back then and it worked for me.
You might want to check out the drivers for it, if it has any available. Incase you're using XP as the OS, go to system configuration or whatever it is called in english. There should be a tab called keyboard where you can configure the delay of the keyboard button mashing or whatever, so incase you hold or type buttons you can configure the delay of it exactly for your needs.
This probably won't help but I tried :3