zafira cd/radio memory?

hi i have just bought an 04 zafira, the cd/radio (not standard fit) says alpine on it keeps losing its pre-set stations and cd position like it has no memory every time i turn ignition off, if i take the face of and put it back on while engine running it remembers, just as soon as the ignition is off, any ideas plz, is it the unit at fault or the car?? ta