Delayed keyboard function.

[#1]

I have a very strange fault which has recently occured on my computer, when it comes out of standby the first keyboard stroke is not registering, after repeating it the rest of keyboard activity is normal, it doesn't matter how long I wait I still have to repeat the first stroke. I'm running XP Pro and my system is clean of any malware as far as I know and is scanned regularly with AVG free and Defender.
Any ideas what it could be would be appreciated, regards, Jack.

[#2]

Try a different keyboard.

[#3]

Don't forget to press the any key

[#4]

the keyboard is connected via PS2 and I have tried another keyboard, the point I can't understand is it only happens when the computer comes out of standby, Jack.