New VISTA installation fails to allow backup

Hi -

Just downloaded and installed gpg4win on Windows Vista for the first time. Ran the GPA application, which (as expected) asked me to create a key, which I did, and then when I try to back it up, I keep getting a failure dialog:

GPA Error: An Error Occurred During the Backup Operation.

There seems to be no other diagnostic information.

The system does create the file meant to hold the backup key, but it contains no data – it is zero-length.

Quitting and restarting the program, rebooting the computer, running GPA as administrator, nothing seems to help. Any ideas?

Many thanks in advance.