Hi Tom,
Thanks again for the reply. Here is that header:
#Software: Microsoft Internet Information Services 6.0
#Version: 1.0
#Date: 2009-09-14 05:09:51
#Fields: date time s-sitename s-ip cs-method cs-uri-stem cs-uri-query s-port cs-username c-ip cs(User-Agent) sc-status sc-substatus sc-win32-status
Sorry for not posting that in the first place, I see now that it ids what each code is. As you suspected, the 64 is the win32 status.
I read somewhere else that IIS will log a 64 if the client resets the connection instead of sending an ACK. This leads me back to questioning the behavior of the client and the difference between the "Microsoft-WebDAV-MiniRedir" and "Microsoft+Data+Access+Internet+Publishing+Provider+DAV". I'm still trying to determine how the client determines which of these to use.