>Here's the scenario:
>Say a global (named) mutex is created by a web service running under the auspices of IIS. Since IIS is a service, it excludes by default all but the local system for ALL_ACCESS security to the mutex. The doc also states that all calls to CreateMutex request MUTEX_ALL_ACCESS security to the object. Now I've got an application that tries to acquire the mutex by creating it. It fails with an "access denied" error. I'm assuming that the app does not have the same security permissions as a service.

You may have to review under which security context you're actually running. I would guess if this is under Web Services that the context will not be SYSTEM but rather ASPNET or whatever you have configure you Web.Config file. ASPNET likely doesn't have permissions to set the mutex by default unless you elevate the permission set...