[BackupExec2012] Error when backup some Exchange Databases

Hello all,

I have a problem to backup some Exchange databases on our Exchange 2007 cluster server with this error :

V-79-57344-6404 - Snapshot Technology: Initialization failure on: "\\mail\Microsoft Information Store\DB1". Snapshot technology used: Microsoft Volume Shadow Copy Service (VSS).
Snapshot technology error (0xE0001904): A failure occurred querying the Writer status. 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 prepare snapshot operation (8).

The same problem occurs when I retry the backup, on the same databases (global job or specific job). For the others databases, no problem.

I'd like to avoid to restart the mail server.

Thanks a lot