I was messing with some stuff yesterday, and I made a merged object esp, a merged dialogue esp, and a merged leveled list esp with TESTools.
After I did this, my save won't load, even if I disable all of the merged esps. I get a host of MCA related errors. The first one is "could not locate global script 'mcac_startup'"
Same thing happened to me a few years back when Testool wrecked my game in the same way, At the time my savegame wasn't too far advanced so i did a clean install of the whole game and started again from scratch. However it is commom knowledge that Testools merge functions don't work and you should use alternative utilities for merging lists such as Wrye Mash.
Delete those merged esps you made with Testool, and try installing MCA again and see what happens.