Hi Mark, Thanks - they are both 16bit; the one that works is 22.1 kHz, bitrate 56 kbps, the ones that don't work are 44.1 kHz, 128 kbps. But we've delivered many other modules with files at 44.1/128 with no issues. Could that cause a problem on this one computer, or is there something else in the encoding that would be worth looking at? thanks! Curt