MP3 files are decompressed and decoded "on the fly". Unlike a WAV file which is simply read and output.
The upshot of this, is that MP3 Files are very processor intensive to play. If you are working your PC hard with graphics, and also making it draw the desktop, It's quite likley that the mouse movements are pushing the processor "over the edge". One of the first things to suffer from lack of processing time, is the decoding routine for MP3 files.
I suggest you try your software out on a different PC and see what happens. Lots of modern Sound cards actually decode MP3 files on thier own, without having to tax the processor, so this should make the differance.
To prove the theory, try running your program with SYNC OFF at the top insetead of SYNC ON. This forces DBPro to use the minimum possible CPU time, and should free up enough CPU to allow clean MP3 decoding.
Hope that helps
