LG UX565 will not recognize MP3 files that other...

Question

I purchased a 4 G micro SD card for my new phone (UX565). Quick start instruction say that I have to have a card and a USB cable to download MP3 files to my phone. In the Manual there is a section that says if I have a card reader, the USB cable is not necessary. I have sandisk equipment. Files record on to the chip and will play on other phones, but my phones will not even recognize the file on the chip. Whats up with this?