NetMon 3.3 has just been released, with a number of new features. One of my favorites this time around is the ability to add comments to a frame. Also, keep in mind that protocols are evolving and having the latest NetMon can help. For instance, only the more recent versions of NetMon include an SMB2 protocol parser that can properly show more complex frames like compound SMB2 requests and responses.

Get all the details, including a complete list of new features, a download link and a picture of the NetMon team :-) at
http://blogs.technet.com/netmon/archive/2009/04/22/network-monitor-3-3-has-arrived.aspx