What brand grip are you using? I just had to replace my Meike grip (replaced with Nikon grip, I know expensive but good) due to battery draw and would cause the light to come on randomly also.... If it happens again with the grip installed, try just taking the grip off to see if that corrects the issue. If not, then I would agree and look at the memory card pins. Also another thought would be if the lens contacts needed cleaning and by moving camera around to remove and install batteries, may have restored contact for now. Just some thoughts to try if the issue comes up again.