Creating a new server in BO XIR3.1

Hi all, just installed XI R3.1 + SP3 on a Solaris platform. But when I tried to create a new webi proc server from within the Central Management ConsoleI found that the option was disabled. We are using a 3 CPU license, which I originally thought was the problem, but we put in an evaluation license and it made no difference. Why can't I create a new server ?