Topic Last Modified: 2008-02-05

Users may receive an error that tells them that Outlook Web Access is unavailable when they log on to Microsoft Office Outlook Web Access on a computer that is running Microsoft Exchange Server 2007. In addition, the application logs on the Exchange 2007 Client Access server may show that ISAPI filters are failing to load.

For example:

Event Type: Error

Event Source: W3SVC-WP

Event Category: None

Event ID: 2214


The HTTP Filter DLL C:\WINDOWS\System32\RpcProxy\RpcProxy.dll failed to load.


This issue can occur when a 32-bit version of ASP.NET is installed on a Client Access server that is using a 64-bit version of Microsoft Windows Server.

The 32-bit version of ASP.NET may have been installed with another application, such as the Microsoft .NET Framework version 1.1, or with Microsoft SharePoint Portal Server.


To fix this problem, follow the instructions in Microsoft Knowledge Base article 894435, How to switch between the 32-bit versions of ASP.NET 1.1 and the 64-bit version of ASP.NET 2.0 on a 64-bit version of Windows.