I realize this was some time ago but I am seeing this issue now that NMCI is rolling out Windows 7 devices in another domain where users need to access our resources. No problems from XP machines in their domain. Exact same error as described by you. Any chance you remember what you ultimately did to fix this? My cifs.LMCompatibilityLevel is at 1 so it should be accepting everything from what I understand? Cifs.signing.enabled is also on.