Ok. Browsed the forums and could not find a concrete answer. I just purchased the current low end imac and a My Book Studio Edition 750 GB external hard drive. Found the dreaded blue paper that read: Notice: Mac Leopard OS X 10.5 Users. Tp upgrade this product to be COMPATIBLE with leopard...blah blah..I thought and hoped it would be plug and play. So I followed the instructions. For some reason there is no longer the FIRMWARE Update. Now, TM wont do an hourly backup if the imac sleeps. HELP.... Thanks.