Hi all. I'm using an iMac 11,1 2.8Ghz i7 running OSX 10.6.8, with 8GB RAM, no other upgrades. While using my usual three programs - Adobe PS, ID and LR, plus Safari and stickies etc, I'm noticing a lot of lag in seeing the effect on screen when I'm adjusting levels or curves in PS (on an adjustment layer) Happens most when I have about 10 images open, each about 40-80MB. Wondering if it's GPU or RAM that's causing the problem? Anyone got any ideas? Thanks in advance.