I can't move objects I imported an object into my model, and now I can't move anything! I can scale and rotate just fine, but whenever I try to move an object, it acts like the arrows aren't even there!
From your question it seems you use 3D manipulator to translate objects. In this case make sure proper mode of manipulator is checked - arrow as its icon for translating. You can choose multiple manipulators by clicking on icons with Shift.