Hello or more like HELP!!!!

I've got a audi a4 on 2003 with a navigation plus system. i had to disconnect the battery and now the sat nav won't work. It says Safe Locked. I didn't even get chance to put my code in. The unit won't do anything. I've taken the unit out and disconnected it and put it all back and still won't work. does anyone have any idea's to help me out please its driving me mad.

Thanks

Michael