My first thought is where is your audio stored?
If Myriad is unable to get to the files, it will be unable to play them.
Are you storing them on a NAS device? We have seen quite poor performance from some NAS interfaces, and sometimes they just randomly disconnect themselves.. Not a problem if it is a word document or a picture, but when we are streaming the files directly off of the data source, very problematic, this would also explain why when you load the file into Cool Edit, you are loading it completely into memory.
Broadcast Radio Ltd