Exchange 2007 Server EXCDO Hatası

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Aşağıdaki hatayı nasıl düzeltebilirim. Yardımlarınız için teşekkürler. 

Event Type: Error
Event Source: EXCDO
Event Category: General
Event ID: 8206
Date:  7/28/2010
Time:  9:16:53 AM
User:  N/A
Computer: Exchange

Description:
Calendaring agent failed with error code 0x8000ffff while saving appointment.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp .
Data:
0000: 48 72 53 61 76 69 6e 67   HrSaving
0008: 41 70 70 74 3a 3a 48 72   Appt::Hr
0010: 43 68 65 63 6b 50 61 74   CheckPat
0018: 74 65 72 6e 20 66 61 69   tern fai
0020: 6c 65 64 2e 20 4d 61 69   led. Mai
0028: 6c 62 6f 78 3a 64 69 6c   lbox:xxx
0030: 65 6b 2e 67 75 72 73 6f   xx.xx
0038: 79 40 62 64 6f 2e 63 6f   x@xxx.co
0040: 6d 2e 74 72               m.tr