UIView rotated by 45° disappears?

You need to stop adjusting the frame after the rotation, it causes undesired stretching to the transform matrix, I'm unsure to the formal reason why, but it has something to do with Apple using their own matrix system rather than traditional matrices to represent 2D/3D translations/rotations/scale. I was having the same problem the other day, to fix it, instead of rotating that view, I just made it a container with the actual view I wanted rotated inside, and rotated that.