When you start the Microsoft Exchange Information Store service on a Microsoft Exchange Server 2007 server, you may find the EXOLEDB component is not initialized successfully. Additionally, the following event is logged in the Application log:
Note Even though the Exchange Information Store service is started, there are various issues caused by the unavailability of the EXOLEDB component.
This issue occurs because there is a key under the HKEY_CLASSES_ROOT path and the default value of the key is not of the REG_SZ type. However, Exchange Server 2007 makes an invalid assumption that all default values of the keys under the HKEY_CLASSES_ROOT path are of the REG_SZ type.
To resolve this problem, install the following update rollup:
972076 Description of Update Rollup 2 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.