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