First off, if your radio has a code, make sure you know it or have it writen down somewhere. Going about getting this code is a pain in the royal hiney.
I wouldn't know where to start with this, aside from maybe check all power and signal connections. The most important thing you can check is connections to make sure they are plugged in. Take out and reseat if you have to. I'm not too familiar with the later E32 radio's.
Best I can suggest is head on over to the
Roadfly E32 forums...there's some excellent chaps on there who might be able to help ya out. Registration is free. And tell 'em 'bimmerman750il' sent ya!