Richard Jackson wrote:
So your equations are not all independent.
Sorry I have read: "the number of equations must match the number of unknowns" not "the number of independent equations must match the number of unknowns" 
Richard Jackson wrote:
Does the solver in Prime always always let you get away with that, or did you just get lucky in thins one case?
My answer on your new question is old: "Not allways".
Second case - the number of unknowns > the number of [independent] [nonlinear] equations
