Why are some apps keep running in OS X even if I quit them? At least three apps are now doing the following:


In its menu, I click on quit
It starts quiting but
then never finish quiting. 


I can switch to it. The icon in the dock bar shows it is running. The menu is there, but the Quit option is disabled.

What's going on?

It is happening with:
- Microsoft Word
- Skype
- Another one, not by Microsoft

After an update, Word is not doing it anymore. It is puzzling.
It is due to bugs. Most likely in those programs, or in the OS X system. Essentially the program never completes the "Quit" action, so it doesn't exit and thus stays running.

Another cause could be hardware error - such as a non-responding hard drive. If that was the case, you would be seeing problems everywhere and not just with the Quit menu option in a few programs.

If you want to investigate the specific cause on your machine, I would suggest using dtruss to see what system calls the application makes as you hit quit. It could for example be hanging waiting for a mutex/semaphore, or similar - suggesting a deadlock or livelock. In other words, a bug.