Error -50 could not synchronize record to exchange server

[mother]

Hello

I get the error in when the Entourage X calendar tries to Sync with our
exchange 2003 server.

Error -50 could not synchronize record - "the calendar appointment" to
exchange server

This therefore none of my meetings are appearing on exchange so no one
can see if I am busy etc.

I have checked and patched entourage and have set the busy/free server
to the exchange server/public

Have rebuilt database

Any other ideas please

Thanks brett