We use Zara Radio at Access America for all our syndicated and regular scheduled programming. It works like a charm! The IMS add-on is great for scheduling music if you need to select gender or tempo. In other words, it lets you schedule three fast songs, one slow song, etc. The "Random" or "Shuffle" feature in Zara is not made for that.
Here are some points to pay attention to:
1) As the previous poster pointed out, make sure you have the right file path.
2) Some audio files are protected. Right click on the audio file, go to Properties and see if your computer is "allowed" to play the file.
3) Check the settings in the Events list. Make sure you have the right time and date.
4) If it is important that the file plays, make sure you have High Priority and Immediate checked.
5) Make sure you have no other High Priority and Immediate files playing at the same time.
Hope this gives you some pointers to solve the problem.
Ralf
http://www.access-america.net 
