Vienna Suite 1.1 needs a bit more ram than before. I have expected this. I am using Omnisphere on my macbook with ext. usb drive and tested the same with loading proceedure with 2GB RAM and after 4 GB RAM. The point is that you need more than 2 GB RAM in your computer (recommended 4GB minimum) to run Omnisphere 1.04 and Suite 1.1 without any problems by using more than 12 tracks with omnisphere at the same time with each inputting one Suite Reverb. My MacPro-System is working great and it needs with the same template 10 percent of the first core-bank from the 8-core system; the other banks are activated lower than 1 %.
Believe, after Snow Leopard all your core- and ram-problems will be solved, if you are using a Quad or 8-core system.
Tip: I don't like Altiverb(it is ported like Adobe products to Mac), so I changed to Arts Acoustic Reverb. Try it; may it is an alternative solution for your problem.
Nico.