I have the same problem. Managed 8gb on a 128 card. I can put in the music that won't work on a different card, and it works fine. So in other words, if Nickleback is over the 8gb, it says sorry, can't play format, but I can put the same song on a different card and it works fine. It is not the card, it is not the file, it is something with the phone. Sometimes it does not take file transfers well like it garbles the first portion of the music, or it will only play 1 or 2 seconds over and over and skip to the next. Again, I can fill up an 8gb card with anything that does not work that I copied to the 128gb card and it has no issue. I have also copied the files to the phone and it plays there fine. move it to the card, and it says cannot play this format, so again, proof it is not the file. I see a lot of similar or the same complaints but have yet to run across the solution.