Agreed. Sounds like piston damage ocurred during brake pad installation.
However, unless you had the unfortunate luck of messing up BOTH left and right pistons, it's going to take some troubleshooting to determine the problem.
First, I'd try detaching the vacuum check valve from the power brake booster, and see if the pedal rises or the front brakes release. If not, remove the calipers by their slide pins and see if the pistons are seized. You know where to go from here.
Be aware that there are a LOT of shady-engineered/machined parts out there. I've had the misfortune of having brake pads that were too thick with rotors that were too thick as well. The results were similar to your experience, but I couldn't even fit the calipers to their mounts because the components were so badly made!
Lesson learned: always pay more for quality parts and the assurance that they'll work.
I'd suggest using Performance Friction carbon metallic pads if it's determined that the calipers are all right and there aren't any other factors causing lockup. They're a little bit thinner than most semi-metallic pads when new.