I have been setting up Exchange Server 2007 for a client this weekend. Everything has been proceeding fairly smoothly, until I tried to test out Outlook Web Access. When going to the server from my browser, I would receive a “Service Unavailable” message.

Event Log gave much more information, thankfully:

Event Type: Error
Event Source: W3SVC-WP
Event Category: None
Event ID: 2274
Date: 3/2/2008
Time: 3:18:41 PM
User: N/A
Computer: xxxxxxxxxx
Description:
ISAPI Filter ‘c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\\aspnet_filter.dll’ could not be loaded due to a configuration problem. The current configuration only supports loading images built for a AMD64 processor architecture. The data field contains the error number. To learn more about this issue, including how to troubleshooting this kind of processor architecture mismatch error, see http://go.microsoft.com/fwlink/?LinkId=29349.

The link didn’t help at all. Searching for “W3SVC-WP 2274″ on Microsoft’s support site also didn’t help. Thankfully, Google saves the day.

The fix is quite simple. Follow the directions in this link and OWA should start to work properly again.

Update:  This is a known issue when Blackberry Enterprise Server is installed on the same box.  See this link.