The Microsoft Exchange Information Store service stops responding on a Microsoft Exchange Server 2007 server. Therefore, clients cannot access to mailboxes which are located on the Exchange Server 2007 server. Additionally, If you monitor the RPC Averaged Latency of MSExchangeIS in Performance Monitor, you find that the value of the RPC Averaged Latency is very high and will not drop.
This problem is caused by a deadlock in the store.exe process.
To resolve this problem, install the following update rollup:
979784 Description of Update Rollup 3 for Exchange Server 2007 Service Pack 2
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.