If, like me, you decided to go installing stuff off the Web Platform Installer 2.0 Beta, you may start getting IIS7 Application Pool lockups, and general non-responsive behaviour.

Digging through the Event Log, I was getting this:

Faulting application w3wp.exe, version 7.0.6001.18000, time stamp 0×47919413, faulting module ntdll.dll, version 6.0.6001.18000, time stamp 0×4791a7a6, exception code 0xc0000374, fault offset 0×000b015d, process id 0xad0, application start time 0×01c9c03e217b6255.

Unfortunately, this doesn’t really give any useful information, and the search results seemed to indicate that it was PHP at fault. I was running PHP, but this happened even when PHP was disabled, and the request was for static files.  PHP was also running just fine under other Application Pools.

After much faffing about, including creating new application pools, even pulling out DebugDiag and getting memory dumps, I was still lost – so I started disabling IIS Modules as a last resort.

I didn’t have to go too far: Removing DynamicIPRestrictionModule caused everything to start working again.

Ironically, this module is supposed to prevent Denial of Service attacks.

Tried reporting this as a bug in Connect, but it doesn’t seem to be supported via there – only via the Security forums on the IIS Site. Keep an eye on this thread to see if there’s a resolution.

Update: Microsoft responded to me, and confirmed it’s a bug in the application, it’s queued for fixing in a later release.