An issue exists with this pre-release version of the Update Rollup 4 for Exchange Server 2007 Service Pack 1 (KB952580) with regard to the Exchange Web Service (EWS) that creates the potential for a continuous crashing cycle. The final version of this update will be released shortly and we recommend customers who have not already installed the update to wait to do so. For those who have already installed the update, we recommend uninstalling this version. Once a new the final version is made available, all Exchange 2007 SP1 Installations with pre-release version of Rollup 4 installed will be offered the final version which will install over the pre-release.

Identification of Rollup version via Add/Remove Programs: To identify the version of the Rollup that you have installed, press the "Click here for support information" link on the rollup, under your Add or Remove Programs applet in Control Panel[…]

Full Article