given that the mp3 standard only supports 2 channels at most, what is probably happening is that your sound device is mapping the stereo file into 4.1 channels and playing it that way.
the main difference between media player and our software is media player uses the DirectX sound drivers, whereas we use the standard Windows drivers. That is probably why you are getting this issue, your sound card's standard Windows drivers are not letting you play in a 4.1 environment.
2) wavepad has no "pause" feature, you are hitting the "scrub" button which plays a very small bit of audio at the cursor location in an endless loop.