10.1 ArcObject SDK crash on SdeWorkspaceFactory

Question

I have very weird crash without any error message on my WCF code on ArcGIS 10.1 SP1. If WCF Service is running as local admin application pool on IIS it works without any problem. As soon as application pool user changes to limited access (IIS_IUSR), beliow line crashes withoug any log or error message. Same code ran fine till ArcGIS 10.0, since it has no logs or any information, it is impossible to workaround. My code is bound with EngineOrServer with proper licensing initialization right before this line of code is being called.

IWorkspaceFactory workspaceFactory = new SdeWorkspaceFactory(); 
IWorkspace workspace = workspaceFactory.Open ("connection goes here");

nicogis · Answer

here you can see why you need use activator: ArcObjects 10 .NET SDK Help

JonMorris2 · Answer

If you need to use an activator, why does Esri produce samples that do not use this method?

Set Data Source Snippet

And why does it sometimes work? E.g. calling

IWorkspaceFactory workspaceFactory = new SdeWorkspaceFactory();

at 10.2 works for me, but at 10.0 it does not.

Also I can call new FileGDBWorkspaceFactoryClass() at 10.0, even though it is also a singleton.

ChrisLim · Answer

Thank you for responses. I finally can get back to this problem from other tasks.
I believe this is permission problem more than 64bit issues. Beside crash on SdeWorkspaceFactory, it's crashing on ESRI license initialization when application pool user is in IIS_IUSRS group only. As soon as I put app pool user to administrator group, it works.
I am using Licensing code example from http://resources.arcgis.com/en/help/arcobjects-net/componenthelp/index.html#/LicenseInitializer/004800000005000000/ 
and 
http://resources.arcgis.com/en/help/arcobjects-net/componenthelp/index.html#/Program/004800000226000000/

Program just crashes this line on the LicenseInitializer.cs above if only user is in IIS_IUSRS group, it works if user is under adminstrator group.  It's on line 214 from the example code.
esriLicenseStatus status = m_AoInit.IsProductCodeAvailable(prod);

No logs or exception beside application log below.
Faulting application name: w3wp.exe, version: 7.5.7601.17514, time stamp: 0x4ce7a5f8
Faulting module name: AfCore_libFNP.dll_unloaded, version: 0.0.0.0, time stamp: 0x4dde4452
Exception code: 0xc0000005
Fault offset: 0x5368dc80
Faulting process id: 0x16d4
Faulting application start time: 0x01ce3ab0a5291e51
Faulting application path: C:\windows\SysWOW64\inetsrv\w3wp.exe
Faulting module path: AfCore_libFNP.dll
Report Id: 037fddf5-a6a4-11e2-a100-005056140de9

Thank you for help in advance!