When you say "posts a standard query" can you be more specific? That does sound like a DNS issue, since reverse lookups are done by reversing the IP address octet order. Are you using DHCP? If so, does the router report itself as a name server when it issue a lease? Or, did you configure the cRIO to use the router address as the DNS? I haven't used the Linux-based cRIOs so I don't know what the setup is for them, I'm just familiar with the PharLap and VxWorks options.
Of course I could be wrong about this; it might help if you post the relevant bit of the wireshark capture.
