I upgraded this past week to the following:

AMD X2 4400 dualcore
Gigabyte K8N ultra 9 Motherboard with nForce4 drivers
2GB of OCZ 3700 RAM
2 74GB 10k rpm raptor HDs -SX on one, Giga on the other.

I am running Cubase SX 3.1 and Gigastudio 3.12 in rewire mode on the above PC. I have an RME Fireface 800 using 1394b. I have two other PCs that use FX Teleport with several VST instruments all on a gigabit switch.

I had everything working fine with my old master PC which was a P4 3,2Ghz on an Intel 865PERL MB with 3GB of PC2700 RAM. This leads me to believe it has something to do with rewire and dualcore CPUs.

Here is what is happening:

Cubase SX plays perfect as long as Giga is not connected via Rewire.
Giga plays perfect as long as it is not connected to Cubase via rewire.
However, when I link them together via rewire, the CPU meter in Gigastudio goes crazy and spikes up and down cutting out.
All other connections to VST instruments either straight to Cubase or via FX Teleport works fine. Only Gigastudio is causing these problems. Lowering buffer settings on the Fireface, (I started at 256) , makes it worse, and raising it helps a little, but it still constantly spikes the CPU. If I turn off rewire in Cubase with both programs running, the CPU meter stabilizes, but I obvioulsy can't use Gigastudio. I've tried everything I can think of over the past few days, and I need to get back up and running so I can get my work done. I've spent three full days with this and I can't afford to keep idle.

Please, I need help with this. Has anyone experienced this? Is there something I am missing?