Different lines colors when vertical and horizontal

I recently got a 42" tv to use as my monitor at work. My problem is that when I draw a green line horizontal it is bright green, but when I draw a green line vertical, it is a drab green (sort of olive green). Red seems to be worse because vertical looks very similar to color 14, which is a color we use often. My graphics card is a NVIDIA GeForce GT 120 and I have updated the driver. I have gone through and calibrated and adjusted the colors but nothing has worked. Is there something I'm missing or do I just have to live with it?

Thanks for any help in advance.
Jared