Custom Query Designer

Hi,
I'm having some trouble with implementing my own Query Designer.
I have built a control that implements the IQueryDesigner Interface
and register it in the RSReportDesigner.config file.
However Visual Studio never calls it. When I click on the Generic Query
Designer Button to switch between the Generic Designer an my Custom Designer,
The Designer window simply Reads
"The Query could not be loaded."
"Verify your connection string and query string."
I have tried attaching the debugger and I can break on the other Data
Extension classes I have implemented. So it appears that Studio is erring
before it gets to loading my Control. Everything else works fine if I run it
through the generic query designer.
I have also tried uninstalling and reinstalling Reporting Services thinking
the Designer may be broken, but this hasn't helped.
Unless someone has a better Idea, I'm going to resort to reinstalling visual
studio.
Any Ideas?
Thanks
Adrian B.Testing the Query Designer Code on another machine has not helped. So
re-installing Visual Studio will pointless.
I am currently at a loss for where to go with this.
Does anyone have any ideas at all?
Adrian B.