NAS is consuming user sessions

When the Microsoft Dynamics NAV 2009 Application Server (NAS) runs under the Network Service account, the NAS may to try to repeatedly restart. In this situation, the restarts of the NAS consume user sessions. Eventually, this will cause  the users to receive the following error message when they log on to the system …

“Your program license does not permit more users to work simultaneously. Wait until another user has stopped using the program. Contact your system administrator if you want to allow more simultaneous users on your system.”

This problem occurs in the following products:

  • Microsoft Dynamics NAV 2009 R2
  • Microsoft Dynamics NAV 2009 Service Pack 1 (SP1)

The issue is caused by a change in the operating system between Microsoft Windows Server 2003 and Microsoft Windows Server 2008 with regards to how security accounts are viewed.  The easiest way to correct this issue is to change the NAS service login from NT Authority\NetworkService to a Domain Account.  Once the service login account is changed and the NAS is restarted the NAS will only consume one user session as expected.