PP5.5 very slow on brand new iMac

I have seen a number of threads similar to this, but none have been helpful.

 

I purchased a brand new 21.5″ iMac late last year.

Processor 2.8 GHz Intel Core i7

Memory 12 GB 1333 MHz DDR3

 

I installed CS5.5, and found it to be pretty slow. So I got some more RAM. I now hav 12GB of RAM. I saw an improvement, but it’s still really slow. Premiere is the worst. When I press play, even on low-res video footage, it often takes a couple seconds to start playing.

 

I clicked Project Settings, and for Renderer, the “Mercury Playback Engine Software Only” option is grayed out.

 

I looked at some threads… and apparently I have to manually set a graphics card or something like that? I know nothing about that.

 

I have finally had enough of this. Very frusterating. I was sold in PP5.5’s speed, and it has been extremely slow.

Any suggestions? Thanks!

via Adobe Community : Popular Discussions – Adobe Premiere Forums http://forums.adobe.com/thread/1118413