With after 7 on intel, memory issues were a dissaster, CS3 is a lot better but I find a lot of times
RAM “fills up”. Do you Purge the memory? (since you’ve said to be new) edit-purge-all, normaly does the trick. Another thing is the size of the comp; a big comp cost after a lot to preview, you can pre-comp in a smaller one, size down and enjoy full-length previews.
vanderzee.tv