RUMBA/A4988s w/24V result in motors working erratically

I am upgrading from a 12V power supply to a 24V power supply on my RUMBA system, and have a 24V E3D and heated bed. I use Repetier, and have tested the hot end and heated bed at 24V, no issues. I have Pololu A4988 motor drivers, and when I attempt to move any of the motors (X,Y, Z, E), I get erratic motor behavior, not at all what I expected. I suspect I am hitting some sort of current limit with the pololus. Is there some method I should follow to recalibrate these pololus to be able to power them with 24V? I know their input voltage range is 8-35V - it just seems like something isn't set right.

Thoughts/help?

Thanks,
Rob