Bright child can't retain letter names?

Wow! I was just browsing through here as we have been starting to learn letters with our son (adopted 11 months ago) and it is exactly the same thing. We just don't know what to do. We worked for days with the Leappad fridge letter thing... nothing (we were just working on A and B)... we moved on to him tracing and writing the letter. He seemed to learn A and then B (three days of practice). We skipped one day this weekend and now he has no clue was a B is... you can point to any letter and he says A... I am so sad and anxious :( and I just don't know what to try next... what will school be like if he can't learn his letters. Any and all advice is REALLY WELCOMED!!! Tracie