SD Card and music help PLEASE RESPOND

Have you formatted the card in the phone? If not, try that. How many files are on the card? Is it full of music and such? That could cause the phone to lag (accessing a lot of music caused mine to lag a bit).

As far as the Mac issue, I'm not sure. Try putting the phone in USB Mass Storage mode when plugging the USB cord into your computer. Your computer should then see the phone as a removable usb drive. Double click on it and you should then see your music folder. Let us know if you have further problems.