Hi,
You can use webdiagtool to get the traces for issues in SPNego configuration. Thiis tool really helps you to trace the error. Please refer to note 957666 for diagtool.
Please refer to the following blogs on SPNego troubleshooting
Configuring and troubleshooting SPNego -- Part 1
Configuring and troubleshooting SPNego -- Part 2
Configuring and troubleshooting SPNego -- Part 3
Regards
Veera