Phantom keystrokes (with 2 keyboards)

Hello again, good people of THG
..another day, another computer problem.

This time its wireless keyboard woes on my brothers HTPC. He originally had a cheapo Belkin wireless keyboard with its own reciever (RF) and it was a tempremental pain with repeating keystrokes (press once, 10 appear etc). So he "invested" in a Microsoft MCE keyboard (IR) to use with the IR reciever built into his Antec Fusion case. Sometimes it works perfectly, sometimes it refuses to work at all and sometimes it creates phantom keystrokes (maybe 1 in 10-20) with the wrong key appearing. Nothing in the line of sight, tried different angles, distances, no joy.

We're confident theres no other equipment in the room interfering with the signal but who knows.

Any suggestions on how I might be able to remedy this?

Cheers,
~Sheepy