Microsoft has released a Hotfix for Microsoft Application Request Routing Version 2.5 for IIS7

This hotfix addresses a couple of problems in Application Request Routing Version 2.5. 1) There is an intermittent crash in w3wp.exe process. 2) With Request Consolidation feature enabled, the first request for Smooth Streaming content may not be cached on disk. More details information about this hotfix is in the Microsoft Knowledge Base article, KB2589179.

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