We have been trying to solve this at work with no luck so I decided to try the experts on these forums as a last resort. Our school has iMacs connected to lcd projectors in classrooms and we use them to project the iMac screen contents on a large screen in the rooms for instruction. Everything worked fine with Leopard 10.5.7. Over the summer, they upgraded all of the iMacs to Snow Leopard 10.6.4 and now the projected images are very dark. They are useless for showing anything beyond text. Photos or video clips are so dark that the students can't see them clearly. The IT people have tried all sorts of solutions and updated all of the graphics drivers that they can find for Snow Leopard and for the various graphic cards in the iMacs. If I switch my iMac running 10.6.4 with another one still running 10.5.7, the projected images go back to looking correct, so it's not a problem with the projectors. We have tried all sorts of settings and different profiles on the 10.6.4 iMacs and nothing has worked. The images projected remain very dark and harsh in contrast, as does the entire desktop and dock icons that are also part of the projections. Can anyone please offer some advice on what may be going on and any possible solutions? We are not really able to revert all of the machines back to 10.5.X anymore. Thanks a lot for any advice.