whats wrong with my amp!?

well, my amp that im using for my subs if MESSED up. i was driving, and all of the sudden it cut out. so i went back and checked it out, and well....the amp had power, and the turn on lead had power, but the amp kept shutting off. then i realised, every time it shut off, the protection LED would come on. then the protection LED shut off, the amp would turn on, and immediately it would shut back off. so i pulled the RCA's off, and it stopped. it seems to only happen with channels 3 and 4. i have 1&2 and 3&4 bridged, each going to a 4 ohm sub, so its not a resistance issue. when i plugged the RCA's back in, it would cut out as soon as the outer ring part would come in contact with the outside of the RCA jack in the amp. could my RCA be grounding out? but why then why do channels 1 and 2 have no problem? what else should i check? please help me, my warranty expires in 8 days and i have to make sure its not a wiring issue before i go to them. oh, i jsut remembered, my RCA, at the deck, one of the plugs is broken, like, completely broken. so one of the RCA's has no signal, while the other does. it was working fine for a few days. now all of the sudden it doesnt.

the same thign happends when i do that

well today if igured id take another look. i was back there messin around with the RCA's, and it kept doing its on-off thing. then i said "ya no wut, maybe its a short inside the sub itself" so i took out my old pyle 500 watt sub, adn put that in place of the right sub. it worked!!! yes!!! so i go up to exxon to talk to my friend keith.......3 minutes, the sub goes out. dammit. i go back, adn its not tripping off or anything, just no music, and a little smoke coming form the port tubes. w t f is going on. i have ONE sub left to use, but its liek, 150 watts MAX (it was free). should i try un-bridging the amp? if i cant figure somethign out by tonight, then tomorrow im gonna drop it off at this shop i go to a lot and havce them figure otu whats goin on.

i took it in troday. they said there was nothign wrong with the amp. they said the problem was that i was p[utting too much power to teh subs. they 10" subs iun a bandpass. basicly what he said was that BP boxzes shodul use much less power, because they allow a LOT of excursion. so my subs woudl be flying in and out more than they were intended to, and the voice coils woudl heat up adn burn. sound about right to you guys? he suggested getting a dual 10 or 12 sealed box, i think im gonan go wtih 12's.