Chapter 3 Authentication for FortiOS 5.0 : Single Sign-On to Windows AD : Troubleshooting FSSO
  
Troubleshooting FSSO
When installing, configuring, and working with FSSO some problems are quite common. A selection of these problems follows including explanations and solutions.
Some common Windows AD problems include:
General troubleshooting tips for FSSO
Users on a particular computer (IP address) can not access the network
Guest users do not have access to network