Well I don´t know but I thing taht this is a bug in Blender 2.43 Rc well You can see this problen in 2.42
Well if you have only a Edge (2 vertex) and wuld you like to use knife (ctrl R) you must see this " ERROR could not order loop" but after like taht you can see your 3 vertex (he does do it, after you see Error)
Payatention that you cant see this error if you have a tringle o rectangle or somenthing more that 2 vertex
This belongs in the bug tracker, its nothing todo with python or plugins. but thanks for the report still