I had defined an 'init' method which did nothing in my Model-Glue Controller for one of my controllers. I was getting a very obscure 'Variable CTRLINST is undefined.' message as a result.
<cffunction name="init" output="false" access="public" returntype="void" hint="">
Removing the 'init' method from the controller solved the problem, and the error message went away - leaving me to run my application once again.
I had become so accustomed to putting an 'init' method regardless in all cfc's that If I had not had some prior controller code to look at - I would have been sitting on this error for a long time.
Hope this helps someone out there - Maybe a more appropriate message here would help (framework guys).