help!!! error -45054 when trying to play/download music in iTunes

Help! I've recently bought my macbook pro. I can see my the music i have previously bought on my iPhone in iTunes but cloud symbol next to most music. When I try to play any of these or download new songs I get error message -45054. I have checked and have shared folder in Users which I understand is important for iTunes. I am running OSX 10.9.4. Driving me nuts, could be persuaded to take the whole **** thing back if I can't get this sorted - expected better given the outlay cost!!