After much poking and prodding, the problem was actually packet size.
The M7001 video encoder was is connected to our wowza server via a VPN connection. The VPN overhead results in a reduced MTU, less than 1200 in this particular case. Once I reduced the MTU in the axis encoder, everything behaved properly.
In this case, VLC's awesomeness, in being able to negotiate an alternative connection when the initial connection failed, made it tricky to see what was actually happening.
The MTU settings are also not available by the regular web interface, you can get to it via: