amp goes into protect, audiobahn subs

I have a 97 dodge intrepid.  I have two older audiobahn 12" subs running off a 1200 watt Sony Xplod XM-GTR2022 amp that I got in March.   I have had these subs for four years now and they have held up great.  Only minor problems like a burnt wire here and there.  Recently I have started having a more serious problem.  I can no longer turn my stereo up without the amp going into protect mode.  If I turn adjust the subwoofer volumn on my deck all the way it will still play no problem as long as the stereo itself is turned down.   The second I begin to adjust the volumn, it will go into protect.  I have eliminated the fact that the amp is screwed up becuase I disconnected it and hooked up my old amp and the same thing still happens.  I also took the subs out of the box to check for fried wires, my ANL fuse is good all fuses on the amp are good and all wiring that I can see is good.  Everything is grounded.  Can anybody help me out and let me know what they think my problem is?  Apreciate it. 

it is the subwoffers. once they begin to play at a louder level the voive coils inside are coming apart and shorting putting the amp in protection. get new subwoofers and you will be fine.

Have you checked the voltage at the amp at the point right before the protect light comes on?  You need to connect your meter leads to the power and ground terminals of the amp.