Help!  Anybody got ideas?

I'm trying to find out why my 3 month old Pioneer 1019 receiver is having issues driving my Aperion 5Ts.  I ran this receiver choice by one of the Aperion gurus before i even picked it up and it was recommended, in fact the guy i talked to gave some praise to the receiver.  Running at "normal" volumes things work fine but it shut downs when i edge it up a bit, like -15 to -10.  I've run speakers individually, i've checked wires and rechecked, i've talked to and gotten troubleshooting advice from Pioneer.  I've given them the 5T specs and they're not alarmed with them.  In fact Pioneer had me send it in for service, which i just got it back from.  Problem is, went in for service and came back as no fault found.....and the service center, did it through best buy, recommended i check my wiring, "Unit is going into protect mode. Which means you have a speaker or speaker wire shorting out."  Well i did check again, visually, and sure enough after getting everything hooked up and running, it shuts down after a short stint at -10 playing some Them Crooked Vultures. (good stuff by the way)

I'm using banana plugs for the connections and only the 5Ts manage to shut it down when i run the speakers individually.  The others are a pair of 4Bs, a 4C and an 8D.  None of which manage to bring things to a halt no matter how loud i go, when run individually.  The speaker wire was picked up at home depot at some pt but i don't know how old the particular wires are running the front two, no more than 3 yrs though, some of its newer.  Anybody have ideas?  I haven't gotten back in touch with Pioneer as of writing this, its on the list of things for tomorrow, but was wondering if anybody else has had similar issues with 5Ts and Pioneer receivers or even experience with some other sys exhibiting mysterious issues.

If anybody has anything, that'd be great cause i'm pretty much at a loss for why this is happening, everybody tells me it shouldn't.