When an Exchange Information Store backup is run, the mailbox database being backed up is dismounted. This has been seen to happen on servers running Windows Server 2008 and Exchange 2007.
This has been identified as an issue with the Volume Shadow Copy service and Exchange. The problem is resolved by installing Microsoft Exchange Server Service Pack 1 Rollup 4 or Rollup 9.
Microsoft Exchange Server 2007 Service Pack 1 Rollup 4 is also contained in Rollup 9. This update is not included in Exchange 2007 Service Pack 2 so if you have Service Pack 2 installed but did not install Service Pack 1 Rollup 4 or Rollup 9 you must uninstall Service Pack 2 before installing the updates.
We advise doing the following during a maintenance window as installing the update will temporarily disrupt Exchange services.
If you have Exchange Server 2007 Service Pack 2 installed, uninstall it. If not, skip to step (2).
Install Exchange Server 2007 Service Pack 1. If Service Pack 1 is already installed, continue to step (3).
Download and install Exchange Server 2007 Service Pack 1 Rollup 9 from Microsoft’s site.