I was using my powerbook today (15" 1.67 fully loaded) I added a gig stick a couple months ago giving it 1.5 total, and it was there and showing up on the "about this mac" and in the activity monitor whenever i checked it since then. All of a sudden today i went to activity monitor and it said i only had 1 gig, so i quickly went to about this mac, and it said that i had only 1 gig also! It said that the lower slot was empty (the one with the apple factory installed 512 stick)! I cant turn off my computer right now to open it up and check the RAM, what the heck is going on???