Hi Morphlite,
Hmm, I have the same machine here and cannot reproduce these CPU spikes, unless...
You mention having 2 GB of RAM - which presets have you loaded and where are your samples stored?
Vienna Instruments Presets can be really large and streaming the samples from the internal HD f.i. is not exactly recommended!
I personnally prefer to build my own matrices, especially on the MacBook Pro, and have my content stored on an external FW 800 disc.
Also, what kind of Audio Interface and drivers are you using?
Best, Marnix