When trying to access OWA we got the following url back:
Along with the standard 404 cannot display webpage message.
Windows 2003 64-bit SP2
Exchange 2007 SP3
The background on this issue was that a server administrator tried to deploy a backup agent to the server which required .Net Framework 2.0, however .Net Framework 2.0 SP1 was already installed which caused the backup agent installer to crash. The server admin proceeded to uninstall .Net Framework 2.0 SP1 so that the backup agent installer could resume.
There are lots of discussion posts around this error message but none of the circumstances applied to this situation.
It was not the cause that a Update Rollup was applied to the server with the Exchange setup logs missing from the default location.
It was also not the case that an Update Rollup was applied while IIS was not running.
Nor did removing and re-creating the OWA virtual directory resolve this issue.
Ultimately the resolution to this issue was found in removing ASP.NET from the Windows components and then re-adding the ASP.NET component. It turns out that by uninstalling the .Net Framework somehow ASP.NET became unregistered.
Perhaps somebody with more IIS expertise than I can explain this relationship to me however we were very certain this was the resolution for the reason=0 message in OWA in this circumstance.