Your problem probably has integer constraints. Maybe nonlinear constraints, too. The solver behaves very differently with tose kinds of constraints. See Mixed Integer Optimization and Nonlinear Constraint Solver Algorithms.
For more help, please shw us your option settings and ga call, and tell us what you want to accomplish (setting a generation value to 200 is not what you want to accomplish; you might want to solve a problem to a certain accuracy, or in a certain time, but I find it hard to believe that setting a generation value of 200 is really the goal).
Alan Weiss
MATLAB mathematical toolbox documentation
