Is it possible you have a sample rate mismatch, between Dim Pro and your audio interface?
If so, there are some Hot Keys for Dim Pro that will tell it to use a different Sample Rate:
This post has a BUNCH of key commands for Dim Pro that I had never known about:
http://forum.cakewalk.com/FindPost/2766342 I would suggest checking to see what Sample Rate your audio interface is currently set at, then make sure you get the Dim Pro Sample Rate to match, using one of the above hot keys.
I cannot guarantee this to be your solution, but it is certainly easy enough to check out.
I would suggest you review other settings in Dim Pro, as well, to make sure you are using the output device you really meant to, etc.
And, sorry - gotta do it - is it possible your volume on interface is down or speakers either off or disconnected?
Bob Bone