But then, when I want to open another file by double clicking it from the finder it doesn't respond.
Furthermore when I open a file from within Illustrator, it just doesn't take any action.
Is it possible that the file is open, but that the focus of Illustrator is not on the file you are opening?
I have this same issue with my Illustrator. CS6 Design Standard.
It's not an issue of the focus, I have no other files open.
Moved to Illustrator forum