Why did my mozzarella turn out like ricotta? I bought my wife a mozzerella kit for christmas, and we tried to make it last night. We followed the directions pretty closely. I supposed we could have removed a bit more whey at some early steps. It also got up to 112F instead of the called for 105F before letting the curds form. But it never came together or reached the shiny smooth consistency that the directions called for. It would not hold together well enough to pull / stretch. It ended up like ricotta. It was good, but it wasn't what we were aiming for.

When doing my Christmas shopping, I noticed that some of the kits were for making mozzarella or ricotta, so I assume that the two have the same ingredients and a slightly different process. So what's the difference in process for the two? I'm thinking that's where we went wrong.

The result actually looked a lot like what this cheese making site says will result from using UHT milk, but I checked before making the cheese, and it was just pasteurized (and I just double checked, and it still just says pasteurized).
I have the same problem and went through 3 different brands of milk, thinking they were UHT.  However, after some experimentation I determined what I was doing wrong.  

In my case, after cutting the curd, and while the water was heating back up to 105, we were stirring too much.

The key is very slow gentle movement. Just enough to slightly move the curds, and not disturb them.

"Stirring" will cause you to end up with a nice tasting ricotta, but not mozzarella.