Certain games automatically going into interlaced mode

I own a 2011 Mac Mini, and I seem to have noticed a certain problem with a couple of my games.

You see, I am using an Asus monitor (not exactly sure of the model number) that has a native monitor resolution of 1080p, and my desktop resolution is set to that also. However, when I start up certain games (Civilization V, Hedgewars, ect) my screen automatically goes into interlaced mode (and 30hz), which causes my games to look quite fuzzy and blurry. I did not have this problem when I first bought my Mac, and it's getting rather annoying. Is there anything I do to fix it? I would really appreciate some help.

Thanks,

XTUX345

Oh, and in case it helps, my Mac Mini is the 2011 model with the discrete graphics and 4GBs of RAM.