uC controlled MOSFET based LED Dimmer stops responding
In situations where something has worked for a long time (days) and has suddenly stopped, it can be difficult to tell exactly what happened. As far as flaws with your circuit (that would make it suddenly stop working after a month), the photodiode is the biggest thing that looks weird to me. Not to mention (from a terminology standpoint) "Comm" or Common generally isn't used for "power".

My suggestion would be to put a scope/ voltage probe on the output next time your design acts up. It could be that the power supply had an issue totally independent to your circuit.

If the problem is too sporadic, try simulating your design in something like LT spice and  sweeping operational parameters and temperature to make sure nothing is biased on the limit.