i have samsung a670 and i had done this about 3-4 previously and worked fine.
and then i dont know why i cant do it anymore. i recently switched my package to free txt msgs so i dont know if that has anything to do with it or not
do you need the data cable to set it as your ring tone? I have the music file saved under a folder called "tones" (the phone did this automatically) but there is no way to accually set it as my ringtone, only play it on command.