Troubleshooting Microsoft Network Load Balancing Clusters
This section lists some common issues that you might encounter when using Network Load Balancing (NLB) clusters
http://technet.microsoft.com/en-us/library/cc732592.aspx
Network Load Balancing (NLB) Survival Guide
http://social.technet.microsoft.com/wiki/contents/articles/7329.network-load-balancing-nlb-survival-guide.aspx