I have all my squeezeboxes and softsqueezes on my Linux server (OpenSUSE11.2). I do have ports 9000 and 3483 open on both UDP and TCP. Nonetheless, none of my Squeeze clients can "see" my Linux server. The Squeezeboxes allow you to enter the server address. Controller does not. 

And thus, during setup, you cannot get past the search for devices step. The skip option will not work. You must activate the Controller as a Device to continue. And even then, there is no option on the main menu to select a device!

After a week of frustration , and much misinformation from your support people (who claimed that controller found the squeezeboxes directly, rather than through the server), by accident I found a menu to Add a Library, and was able to enter the ip address of my Linux server. And then, lo and behold, the clients all appeared.

1) You need to fix the issue with Linux servers not being found by clients.
2) You need to change the Controller Menu to search for a server (via ip address) before searching for clients.