It's a relatively recent radio which is why I suspect you've not had many responses to your post. I can only suggest you try to contact Grundig themselves.
http://www.grundig.co.uk/
However, the fault you have may be something much simpler than that- have you tried it on both batteries and external AC power? I'm assuming (I don't know why; probably because my Sony ICF2001D has this arrangement) that there is a separate battery that maintains the clock and the memory.
Alan