Like Scott Martin, I think that your sensor is over ! symptoms are classic. its filters are in gelatin so, with time they deteriorate and... without warning ! Change your sensor for the i1 Display Pro. It is a very good colorimeter/software and... it have a glass filters.
Sorry for my english, I am a french photographer but passionate by Color management !
I have wrote a Smart Guide to Color Management where I speak about that :http://www.color-management-guide.com/calibrate-monitor.html