Activesync Prompting "The following information type on your mobile device has items that have not been synchronized..."

I had been successfully synching my iPAQ to Outlook using ActiveSync 3.7.1
(Build 4034) for a long time when I was suddenly presented with the
following window during the synch process:

"The following information type on your mobile device has items that have
not been synchronized with this computer before.

Informatoin Type: Calendar"

I will ocassionally get the same thing with Tasks and Contacts but ALWAYS
with Calendar.

I have tried the "Combine" option as well as the "Replace" option and I
still get the same thing.

I have warm-booted my iPAQ repeatedly as well as restarted the computer and
compacted my Outlook databases.

This used to work and now it doesn't. Any thoughts?

Your help will be greatly appreciated.

Sincerely,

Jim