NAC102 switching inputs willynilly

OK... I recently (about 3 weeks ago) bought a NAC102 and a NAP180. Im very happy with them so far... But last week, I had a problem where I was running my Gamecube through the TV, then the TV through the Amp. I had left the game on pause, and after a while, the amp kept switching between inputs quite regularly... I found that this only happened when I left the GC hooked up to the TV AV input. I unplugged the GC from the TV, and the problem stopped... This morning, I was demonstrating my new system to my sister, and while I was playing a CD (I had the TV switched on at this time, but no sound as it was on the CD input) it switched inputs again. I have switched my TV off now, and it hasnt switched inputs since... I wondered if anyone else has had this problem??? At first I thought I was sitting on the remote, but checked that and unfortunately it wasnt that simple...
Thanks