I just purchased a 15" MBP, the least expensive 15" model, and Adobe CS6. I was editing on the computer almost all day. After returning to the project after taking a break, I found it was if I was editing on a completely different computer. Premiere hardly could playback through my footage, audio only played some of the times, and the play button was delayed. What happened and how can I fix this?
I think that you'll get better answers if you post some of the specs - OS version, multiple or single hard drives, drive space, PPro cache settings. My first thought would be that you might only have one hard drive, and that the PPro cache filled things up. Just a guess, not knowing any details.