While trying to join a machine which had previously been on a Windows Server 2003-hosted domain to a new domain hosted on Windows Server 2003 R2 (not sure if the change in OS is the cause of this issue), I kept getting “Access Denied”.
C:\windows\debug\netsetup.log it says:
NetUseAdd to \\DC_FQDN\IPC$ returned 5 NetpJoinDomain: status of connecting to dc '\\DC_FQDN': 0x5 NetpDoDomainJoin: status: 0x5
The solution was to fire up
regedit and change the value of
HKLM\SYSTEM\CurrentControlSet\Services\lanmanserver\parameters\enablesecuritysignature to 1, and restart.
Edit: Do this after leaving the original domain for a workgroup, because doing that resets it to 0.