Hi, From the start, >> Common sources of this bug include user marshaling errors for COM-interop or PInvoke, which may corrupt the stack. 1. When working in the unmanaged context, it is worth trying the STAThread attribute on the method. >> ax.LogonAs("User1", "Globe", new NetworkCredential("User1", "pwd", "Globe" 2. Try adding a role for the user with ax32.exe (if it already exists, please post the role). Plus test permission sets and any admin tasks that was done during installation of Ax. 3. It looks like with messages on "marshalling" and Domain usage: Single, it could well be related to the CLR, the GAC and the Dll context. These are vague references that can be clarified if you walk us through your installation type of AX, the CLR version, the roles and permission sets. Jv On Wed, Oct 10, 2012 at 7:58 AM, Mun Wai Chan