Recently upgraded to ICS HoB 246. Last night I was at the gym and listening to music on my bose earbuds with power amp. The music sounded really hollow and the vocals were very quiet. After a lot of messing around I found the 3D audio effects were enabled. Turned it off and all is well. I mentioned this to my dad who just got a Razr M. We found his phone, too, had 3D effects enabled. He definitely didn't do it himself so we think it was like that from the factory.
I would advise checking your phone because it may have inadvertently been switched with the update.... And it sounds like crap.