Macbook Pro mid-2015. El Capitan 10.11.4 Computer uses inappropriate apps to open files. Instead of textedit, it opens Terminal; instead of Preview it opens MPEG Streamclip. Dragged photos result in blank icons. When I change the default apps by the usual method (using the "get info" box), they soon revert to the previous wrong apps. Why, for example, would a file set to open with textedit open a new terminal window instead?? Or a .JPG photo file open with a movie application (MPEG Streamclip), after being set to use Preview? I've mentioned this before here - can it possibly be that I am the first person to ever experience this? Any advice would be appreciated... thanks!