Running 10.3.4 on a 1GHz / 1GB 17" Powerbook, iTunes version v4.5 (31)... when I try to purchase music (any music) in the iTunes Music Store I get an "Unknown Error 11503." Check out the screen grab below.. I've downloaded the iTunes installer a number of times, ran it... I always get the same error. Am I missing something? Has anyone had a similar problem or can anyone recommend a solution? Thanks.