::PlaySound - sometimes doesn't work

The great API function - ::PlaySound, sometimes doesn't actually play the file I'm sending.

How do I know? I've set up a monitor email system, which should play an alert sound when a new email arrives or when the internet connection is down for at least 5 minutes. However, sometimes, after a few hours of running, when some event actually happens, the ::PlaySound function gets called, but no sound is heard.

To get 'round this, here's what I do:
Every 10 seconds, I stop the sound, and play it again. The second or the 3rd time, the sound is actually heard.