Stereo & Electronics - radio error???

My 2001 Suburban has the same CD radio as my 98,99 Camaros. My radio worked fine and then all of the sudden I went to put in a CD and the radio said ERROR and ejected the CD. Now the radio just says ERR the entire time the radio plays and it won't play ANY CDs; any ideas of what may be wrong? How do you know what ERROR code it has?

Is it a Monsoon head unit? Here (http://www.ls1tech.com/forums/5961798-post4.html) is a link to the GM head unit error codes.

Matt