The sound pauses or hangs when I try to play it in MP3 Audio Mixer.

In Mp3 Audio Mixer, click on the File menu and select Preferences. On the Playback tab, click on the Playback Device setting and choose the driver for your sound card. Do not choose "Default Sound Device" or any other option aside from your specific sound card"s driver.

This problem is often caused by programs like Total Recorder, which substitutes its own drivers instead of your soundcard"s drivers.