It looks like the recent Microsoft updates broke ASP.NET / IIS on my development machine. Trying to launch any website hosted on my local IIS server returned a 500 error and the following error message:
Calling LoadLibraryEx on ISAPI filter "C:\Windows\Microsoft.NET\Framework\v4.
And checking the event log just returned a similar error message:
ISAPI Filter 'c:\Windows\Microsoft.NET\Framework\v4.0.30319\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.
After doing a bit of digging around on the web, the solution to this problem was to simply re-register IIS using the following command:
Everything then thankfully burst back into life!