Monodevelop open script problems p17 and p18

I've got a rather painful problem with monodevelop opening a new session (window) each time I try to open a script or double click a debug line.

This prevents me from jumping to the correct line of code and makes a mess of my desktop.
I had this back in 4.3.x days that seems to be fixed in 4.5.x. However, after installing 4.6B p17 and even p18 I am getting this again. I've tried manually picking monodevelop binary, even installed Xamarin Studio and it does the same thing. Any help on...

Monodevelop open script problems p17 and p18