Writes to the non-volatile memory are blocked if the controller ever detects an internal inconsistency. The internal problem most likely resulted from a power spike. Make sure that the AquaController's power cord is plugged into a surge protected power strip. Ideally plug the AquaController AC adapter into a different circuit then your pumps, chillers, or other switching inductivity loads. When an inductive load turns off it can emit a voltage spike of several thousand volts. The AC2 has a max of 20 timer names.
Curt