The error message :
Backup- SRV2 AOFO: Initialization failure on: "\\SRV2\Microsoft Information Store\First Storage Group".  Advanced Open File Option used: Microsoft Volume Shadow Copy Service (VSS).
Snapshot provider error (0xE000FED1): A failure occurred querying the Writer status.
Check the Windows Event Viewer for details.
Writer Name: Exchange Server, Writer ID: {76FE1AC4-15F7-4BCD-987E-8E1ACB462FB7}, Last error:  The VSS Writer failed, but the operation can be retried (0x800423f3), State: Failed during freeze operation (9). Consult your Microsoft documentation for details. Check the Windows Event Viewer for corresponding application or system errors.


In the exchange server event log, there are 4 errors:

Event Type: Error
Event Source: ESE
Event Category: Logging/Recovery
Event ID: 206
Date: 9/23/2006
Time: 11:27:29 PM
User: N/A
Computer: SRV2
Description:
Information Store (3280) First Storage Group: Database E:\Program Files\Exchsrvr\mdbdata\priv1.edb cannot be incrementally backed-up. You must first perform a full backup before performing an incremental backup.

Event Type: Error
Event Source: ESE
Event Category: ShadowCopy
Event ID: 2002
Date: 9/23/2006
Time: 11:27:29 PM
User: N/A
Computer: SRV2
Description:
Information Store (3280) Shadow copy instance 1 encountered error -560 on freeze.


Event Type: Error
Event Source: MSExchangeIS
Event Category: Exchange VSS Writer
Event ID: 9611
Date: 9/23/2006
Time: 11:27:29 PM
User: N/A
Computer: SRV2
Description:
Error code 0xfffffdd0 when freezing the Storage groups.

Event Type: Error
Event Source: ESE
Event Category: ShadowCopy
Event ID: 2007
Date: 9/23/2006
Time: 11:27:29 PM
User: N/A
Computer: SRV2
Description:
Information Store (3280) Shadow copy instance 1 aborted.

The Information Store service hangs and needs to be restarted.