I have no idea what started it, but all of a sudden, when I drag something with the mouse, it scales up and down instead of moving. Anyone know how to fix this?

Normally, you can Scale in the Render window by holding S and moving the Mouse up/down on the Z axis.
So, perhaps your S key is stuck down?

If you cannot "un-stick your S" just close the CS and re-open. It should go back to default functions.