We all love a bit of complaining about Microsoft and then they went out and made sure we’d bitch, by allowing 32bit and 64bit .NET apps with a plugin to IIS, and then not allow them to run concurrently.
The trap I’ve fallen in to is that I am suffering with the amazing Service Unavailable screen on my OWA. The event log is screaming at me with W3SVC-WP errors:
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.
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
Okay, so we know this sucks. Finding the info to fix can be a little tricky so here, fire up a cmd shell and run these 2 lines:
cscript %SYSTEMDRIVE%\inetpub\adminscripts\adsutil.vbs SET W3SVC/AppPools/Enable32bitAppOnWin64 0
The first line allows 64bit only, the second reinstalls asp .NET.
Go take a look at your OWA or Exchange web services and they should be back to normal.