II7: ISAPI Wildcard Extension generates 500 error (0x8007007f)

I've written an ISAPI extension using Visual Studio 2012 on windows 7 that is a very simple passthrough wildcard extension.  When compiled as 32 bit, and with the app pool set to allow 32 bit applications the filter works well.  But when I compile as 64 bit I get a 500 error with the code 0x8007007f.  64 bit depends shows all green.  There are no errors in the event log.  Any help would be greatly appreciated.

Thanks

Marc