I hear distorted noise when I try to run multiple PowerCore plug-ins or several instances of a plug-in. What's the problem?
What you hear is coming from your audio I/O which probably has a wrong PCI latency timer setting which in turn leads to the incapability of providing real time streaming audio to and from your audio I/O. The noise does not happen in the PowerCore plug-in path. Any other device sharing the PCI bus with your audio I/O will bring your audio IO to disturb equally by placing a comparably high load on the PCI bus.
Solution: Adjust the PCI latency timer of the audio I/O and/or you place the devices on separate PCI busses.