OK, I finally dissected the cradle and found out the following:
– On the back of th cradle, there are 4 metal pieces that hold the thread for the screws that attach the cradle to the car-windshield-holder. One of the screws was loose (probably due to the constant rattling the craddle takes when attached to the windshielt), and the respective metal bit had detached itself from its plastic socket and fallen into the device, probably causing a short-circuit.
– There’s a fuse soldered to the PCB, and its blown. I short circuited it and found both the cradle’s and the GPS mouse’s LED to light up when bringing power to the system.
In short: There’s a good chance that my GPS mouse and cradle are still fully functional but I can’t say for sure given that my PDA is still dead. (Anybody got an rz1710 that they’d be willing to sacrifice for a test? ;) ) In either case: If you’ve got a similar GPS system, check the screws on the back from time to time and make sure they’re all safely attached (that way, the metal counterpart inside wouldn’t have been able to fall into mine).
I also tried to open the PDA, but alas it is riddled with those @^$&# ultra-tiny torx screws which I just can’t get to budge. Anyway, I doubt I could fix whatever is damaged in there, and as you probably know, I’ve got a new one on order as well.