@COsgood: the issue you encountered is probably a hardware problem. Here are two things to check: 1) is your sprinkler transformer rated at least 500mA output current? If the current rating is too low, you will have trouble turning 2 valves on at the same time; 2) does your controller have a yellow, disc-shaped PTC fuse? If so, consider soldering a wire across it to bypass the fuse. I’ve received reports that when the ambient temperature is high, the PTC fuse is likely to be triggered, causing the controller to freeze. Having 2 valves open at the same time will increase the chance of this happening. Shorting out the fuse will solve this problem.