I've had a really similar issue happen twice on me.
Both occurred over this last weekend when I was out trying to get some pictures of stars.
I had the camera set up with the battery grip attached.
The camer was in remote mode once, and M.UP mode the second time. Both times it happened in manual exposure.
The first time I thought it was something odd going on with high continuous capture or something similar to do with the remote.
I could only stop it firing by turning the camera off, and even then it continued for some time.
Interestingly enough, the first instance nothing particularly weird happened other than the camera seemed to be taking numerous pictures. However, the second time around the screen actually bugged out and displayed a green set of numbers or something like that.
I managed to capture a short, low quality video with my phone to show what was going on with the screen and the actual shutters going off or whatever was happening.
I'll upload it in a post below this one.
---------- Post added 03-06-14 at 03:12 PM ----------
Originally posted by A.Yzerr I'll upload it in a post below this one.
It's a lot darker than I recall, though it was at night with the only lightsource being quite a few feet away.