Thank you John for your interest but that's not the case.
Anyway I've seen that after some time working with Realband it gets stuck as well.
I don't know what Realband is doing to use 100% CPU because I also work with other programs like Cubase 5, Sibelius or Garritan Personal Orchestra and I don't have any problem.
So I think that I'll continue using Cubase instead of Realband.