Here's a thought - a non-Naim CD player would need an RCA/DIN cable. While these are normally wired for input, is it possible you've got one wired for output? (The five pins are one common ground, two input channels and two output channels - only 3 are connected for 2RCA/DIN cables).
Can you try a different cable?
Hang on, when you listened to the set up at the previous owners was he using a flatcap2 to power the 112x ? if so there might be a fault with the power supply in the 150x supplying the 112. (not sure if thats the right way round, do 150x's power their pre amps?)
Dare I turn the din-din interconnect from the cd around the other/wrong (most likely)? Would it matter?