I replaced the stabdard unit in mine with a Pioneer and experienced no problems at all.
Check you fuses incase you've inadvertantly wiped out a fuse (most likely cause). The swapping of one head unit for another isn't enough to cause these problems, somewhere along the way you've altered/disturbed something else. First port of call is the fusebox.
If you see nothing there, take the head unit out agin, get your head in the dash, and look for wires that have been crushed/disconnected during the install.
You will find something.
