So... This happened again.
I believe it may be related to the
existing documented visio problem as when I launched the project next time, I noticed my work was gone... even though I thought I was following the work around.
The error seems to break connections to the D-tools database. I lost my work again on another project, saw this error. And as I'm rebuilding the project, I was unable to use any of the automated drawing tools, or even launch the Dtools stencil Tree.