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For those of you who don't want to pay for a Mac machine (as in, built it themselves for cost-cutting efficiency) yet are Mac OS afficionados, I've stumbled upon quite a bit of... a fight... but finally found a flawless way to deal with it, if you're running an NVidia card.
1) Install Mountain Lion like you would usually do (I suppose you are well informed since you tilted to "Hackintosh")
2) Run the necessary Multibeast things (from Tonymacx) - EasyBeast install + take the MacPro 5.1 definitions. (VERY IMPORTANT to take those definitions and none else)
3) Install the 10.8.1 update (yep, no 10.8.2 - trust me, it will mess your chances at gaming on Hackintosh up if you do update to it)
4) Download the NVidia Fermi drivers for Mac (304.00.something) and install
5) Before restarting, make sure to run Multibeast again, this time putting the OpenCL patcher for Retail NVidia Fermi drivers.
6) Proceed as normal. Also, don't forget to Time Machine your stuff just in case.
Mine worked flawlessly using this sequence (and ONLY this sequence). Don't install the 10.8.2 update period.