I have Win XP I have used Outlook XP Profetional software

there is no problems in sending mail and recieving.

But I try to made a Calendar entry in a time slot and when I moved the pointer to another time slot, the first entry disappeared and a window popped up with:

Could not save item. The messaging interface has returned an unknown error. If the problem persists, restart Outlook.

I've restarted OL. I've rebooted. I've tried re installing OL. Nothing has worked.

My email, contacts, notes, etc. all work ok. The problem is just in the calendar.

I also have a PDA, and when I HotSync it, everything syncs except the calendar and it says - failed.

If anyone have any suggestions or solutions i will appreciate to him.

Regards
Elango K