Pausing and restarting PPT presentation

[saltandlight]

Using: PPT 2003 in a pretty lengthy presentation. Some slides contain two separate audio clips (MP3), one with music to run for (X) number of slides, the other with the narration for each particular slide. Everything works fine if you simply let the presentation run unassisted; however, there may be times during the presentation when it will need to be paused (but that would be different in each presentation). I know that pressing the "S" key will pause and restart the presentation, but here's the problem: once a musical clip has played for more than a few seconds, pressing "S" will only pause the other elements--not the music. The music clips throughout the presentation all vary, from a few seconds to a few minutes--but the effect is always the same--after more than a few seconds of the clip has played, the "S" has no effect on it. Any ideas?