Places to look for troubleshooting information
The knowledge base is pretty useless.
Go to the hardware documentation, and select the
Network Connect and W-SAM Error Messages document for your IVE version.
If that doesn't help, you can run the
NC Troubleshooting application (in the appropriate program group) which will dump the activity of your network connect session while it is happening; usually there will be a clue in there that will help.