Sounds like amp clipping. If you watch the you tube video from Paul yaffee and Rockford fosgate, they describe how to setup the amp one you install it. One of the things they mentioned it's to turn the the AVM all the way off. If it is on it will cause the amp to"clip" our shut down just like you describe. Try cycling through your audio program until you get to the AVP(AVM) then turn it all the way off and see if it still does this when riding.
I always left the avc on, I like the convenience. I tried turning it off once trouble started but it didn't help me. My pbr 300x2 worked flawless for 6 months until a 4 hr ride on a 98 degree day 80 % humidity. Thats what killed it , I believe.
2010 FLTRX , Stage 1, 13" Madstad, Mono tubes, SuperShox, Heritage style bars. Alpine CDE-HD149BT,Soundstream Picasso Nano Series PN4.520 , 5X7 and 6.5 Infinity Kappa speakers
If I have to explain ,you wouldn't under stand anyway.