Weird Socket Problem with Arduino & cRio

[codes02]

What symptoms are you observing from the cRIO that causes the appearance that it has "locked up"?

Are you certain that the Arduino is still outputing data over ethernet? (relevance of this depends on the above q. From your description about "not actively reading" on the cRIO, this doesn't seem a likely issue, but do check).
On checking this: connect a ethernet hub between the cRIO and the Arduino. Plug in a computer to this hub as well. Use wireshark to watch packets.

Also: what is the network setup like? For example: are you running the Arduino's ethernet through the Router, or directly?