clarion amp issues

I recently bought a DPX11500 Clarion amp (last week) and right up till today I couldnt have been happier with it.I was listening to it at about 80 Precent volume when the bass just cut out. Ill try my best to descibe what happened. When the bass cut out I pulled over on the side of the road to check it out. The amp was still on with no codes (flashing led/fualt light), was a bit warmer than my hand (i could just feel the heat it was producing). The subs were still moving, however very little and irregular. I tried everything with reguards to troubleshooting. Checked out each sub indivdually measuring the resistance of each sub. They were 8 ohms each and at the amp 4ohms total. The amp did not blow the 100amp fuse, and is rated for a 200amp fuse... so overpowering the unit was not possible i do not believe. There was no smoke or smell and i even took off the cover and looked at the board...not a sign of buring anywhere, everything looked new and smelled new...Its just funny how the amp triped no fualts...I do have a question tho...upon looking through the manual for this unit it said the ground for the sub speakers should not share a common ground with the amp...what does that mean? I measured from the ground of the - polarity speaker terminal and the ground of the unit itself and there was 0ohms...I also measured the reistance between the positive and negative termanils with the wires removed and there was no continuity.Anyone have any suggestions as to what happened to this amp...or what could have caused this...