Do you have a dual graphics setup, in particular, an Intel graphic processor? This is common in laptops, but is making its way to desktops too. Usually the Intel graphics is used for "power saving" while the NVidia/AMD graphics is used for "performance". If Terraria is running on the Intel graphics, that may be the problem.
If this is the case for you, try searching Google for "nvidia switchable graphics" to find out how to run Terraria on the NVidia card. I saw a few hits that looked relevant. I don't have an NVidia graphics card, so I can't advise you of the exact steps, sorry.
