I have just recently starting getting this error message with regards to (1)
client in the entire organization.

In researching this problem, it is quite clear that this use to be a
recurring and persistent problem with Outlook.

I have tried to the following with no success...

Checked to make sure cache was not enabled.

Deleted the sharing clients ost file.

Restarted Outlook

None of these seem to have any effect.

We are on Exchange Server 2000, using Outlook 2003 SP3, Windows XP SP2.

Any help would be greatly appreciated.