Using NUD 5.3.2.
Recently installed 10.5.8 (NOT Snow...) and find that my NUD calendar is difficult to read - change in font, size, etc.
Also, Bonjour server's status is 'Looking for server".
It sounds like your server computer's IP address has changed. Here's what you can do:
First, open Now Server Manager and see what it has listed as the IP address and port number.
Then go back to the client computer and create a new file (File > New...), save it (File > Save... make it primary) and then go to Server > Server Connections, and click the plus sign. Switch from "Bonjour" to "IP address" and manually type in the Server name, IP address, and port number that you see listed in Now Server Manager. Then click Add, and then click Done.
Then at the bottom of the window, in the status bar, it should say "Reading from server..." and then, "events up to date." Once it says up to date, go to Define > Sets, and double click on the categories to subscribe to them.
If you're still having the font issue, you can change the font, style, and size by going to Define > Calendar Layouts...