You should “upgrade” to Media 100 i V8.2.3a, which should fix your rendering problem (as long as you work in Media 100 i codec in Producer and you export as self-contained).
Okay, for the 8Core you need to disable 4 processors if you want to work right now. Download the CHUD tools from Apples website and install them. Then you will have a Processor Preference, where you can turn off 4 cores.
The upcoming version should fix this.