Just recently my CD Player (CEC CD3300) started making a popping sound (thru the speakers) after about 5-10 seconds into the track. It only does it once per listening session. This player has, by design, a popping sound when pressing buttons because CEC doesn't use muting circuits at it's output; but this problem is different, it pops after the cd is playing.
Also--don't know if this has any signifigance, but the sound seems to have started sometime after I put a Monster 2500MkII ac thingy in the system. I realize its probably unrelated, but thought I'd mention it...
Already ruled out: