Well, sometimes extraneous pops like that can be caused by problems with the synchronization. Do try different cables with both mics to make sure (borrow some from a friend), and (even though the interface is new) make sure that theres no dust or dirt in it and that the thing wasn't a return and they just sold it you without telling you. (some of those guys can be pretty sneaky like that) ((heres hoping its not a lemon))
if you know someone with a different pre-amp/interface, try to grab it from them for a day or weekend or however long it would take you to test everything out.
i agree with moresound on the phantom power deal, too. they could be cutting out intermittently because of a lack of sufficient power. do you always record with both mics active? if so, try just 1 and see if you get the same problem. plus, if i remember correctly those ensembles are 75dB tops on the gain... but how clean are they? youre pushing it pretty close to the limit there. make sure that you arent getting in the reds. getting in the reds in software (especially nitpicking software like ableton) can really mess your sound up. remember, its better to record too low than too hot.
also, id say stop using ableton live to record with. id switch to reaper or something similar until you can afford logic or adobe audition or protools or the like. (reaper is a fairly cheap and fairly powerful program)
good luck with the problem, i hope you can fix it. i know how much of a pain in the ass something can be when you dont know what it is.