Cannot open more documents if all the others are closed My girlfriend experiences the following strange behavior on her MacBook Pro running on Yosemite. It does not happen all the time but when it does, things are always the same:

She closes all the opened documents from apps like ms-word, Adobe Acrobat Reader or Adobe Indesign and then tries to open a new one from the finder window. It looks like the document will be opened, but it doesn't.
The app is still running but the file is not opened.
Opening it from the File menu still works, though.

When this happens she also cannot close the app neither from the File menu nor the Dock. She needs to go to Activity Monitor and force quit the app.

Any thoughts?
I think this is an option from the dock. Go to System Preferences -> Dock and uncheck the Option Minimize windows into application icon. 

If you not see the Window you have in every Application the Window menu. Choose from there the Option Bring all to Front.