What is wrong with my Nintendo Entertainment System?

I'm having issues getting my Nintendo Entertainment System working.

When the cartridge is inserted just right, the screen shows up, but the pointer just alternates between choices on the screen, back and forth, and no controllers are working (I tried 5 different ones). I have tried the cleaning out the 72 connectors and that fixed my original problem of having a grey screen of death.

Assuming by the use of the word "pointer" you mean perhaps an arrow to select the start of a game, it can either be a controller port issue, or an issue with your game. Try using another game to see if that happens again.