After analysis, I have the following error:
C0150004 STATUS_SXS_ASSEMBLY_NOT_FOUND
I went through the entire list of files called by the compiler (ie. C:\Windows\SysWOW64\inetsrv> "C:\Windows\Microsoft.NET\Framework\v3.5\csc.exe"...
The only file that didn't exist is in bold
/R:"C:\Windows\assembly\GAC_MSIL\System.ServiceModel\3.0.0.0__b77a5c561934e089\System.ServiceModel.dll" /out:"C:\Windows\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files\applications_my_app\e34a7fe0\b4388432\en\App_GlobalResources.snrifx3y.resources.dll" /D:DEBUG /debug+ /optimize-
In DEV and TEST, the corresponding file exists.
This site is .Net 2.0, Classic App Pool.
I've compared as much as I can between the environments where this works, but can't seem to find anything that would hint at why this isn't working in PROD.
The machine was seriously corrupted and had to be rebuilt.