Just to chime in, the Discussion Mr.P mentioned is a bit older, after this the ELC Guys released a firmware update which fixed the bug in Artnet talkin to Catalyst.

I got a Node 4 running with my small Catalyst without issues. Let me point out some things:
Make sure the latest firmware is on the Node. The Firmware comes along with the Software which can be downloaded via elclighting.com. The older Firmware does not allow to put DMX into Catalyst, only out of it.

The appearing Node 91 seems familiar to me, as he still should show the correct IP. If so make sure, that your ins and outs are set properly in the Node.

And further on check your IP in the Mac itself. If you got 2 active Network Connections running the mac tends to use the Internet Connection as primary which will never be an Artnet IP.

And last on, I second the guess for Luminex, these items are really fantastic

Good luck

Rolf
www.chaoscenter.net