What would cause the debugger, when used in its own frame, in either VFP8 or VFP9 (Tried both, same result) to fail to follow the sequential trace of code lines in a program?

Does not happen with every program but I have one that I cannot debug because the debugger skipps right past all the break points wiythout showing any trace and seems locked on one particular FUNCTION in the overall program. What causes this and how do we fix it? /psb