I have the same problem, it seems to be a poor capacitator that was built in those instruments. There is no backup battery that would be easy to replace and solve the problem.I get a fatal error message every time I change the batteries even if it takes less than 10 seconds.
The real scandal for me: if you call the technical support of Palm to address that problem, they want to have a credit card number first and tell you that you have to pay 25 bucks if they can solve the problem!! You have to be desperate to follow such a customer unfriendly policy. There is only one reaction possible, though: consider this when you buy your next handheld or (any other product that also is available from Palm!) I guess nobody wants to get caught with people like this in business.