MS ActiveSynch V4.1 backup problems

[macrophysic]

I have MS ActiveSynch V4.1 on my Dell desktop and have experienced problems backing up my Axim X5.

The Axim has no problems synchronizing with my desktop.
When ActiveSynch executes the subsequent automatic backup, I receive the most unusual error message...

" There is insufficient storage memory on the mobile device to proceed with backup. You can increase the storage memory allocated on the device or remove some items from the storage memory and try again."

I confirmed that the "backup to this file" location under Tools/backup is mapped to my descktop C drive.

The first few backups had been executed OK and a backup file exists on my C drive.
It is only recent backups where this error appears.
I can trace it to no event.
I even tried mapping the backup C-drive location to a new empty folder and received the same message.

Plenty of desktop storage capacity... and plenty of open storage on the Axim (as if that should matter).

Does this sound familiar to anyone? Ideas?

Appreciate any advice.
Paul