I'm unclear ... is this the same computer that you ran the GTX 275 and now you have the GTX 980? In the past there have been problems at times when people (including me) have upgraded a video card and somehow some of the driver/pref or whatever files didn't get completely "dumped" in the process. Might be worth checking if this is on the same machine, just to make sure ALL references & files & drivers of the old card are gone. Other than that, Fran's gotta help you ... but he's good at this stuff ...
Neil