Nikon d5000 -> macbook importing issues

so i got my d5000 in june and ive been using it on my mac but i have gotten nothing but trouble. ive called apple countless times and i have been into the apple store and talked to a genius. none of theyre solutions have helped for more than a week. ive had two separate problems one of them with iphoto where photos will appear blank or altered beyond recognition. and the other is with any mac application trying to import photos comes up with an error saying it could not without any explaination. ive been saving in camera raw .nef format and i use a sandisc ultra 8gb memory card. any advice would be greatly appreciated