Something odd is happening on your system if you're getting this message and after the other issues too.
Please (!) can you list your exact version of OSX and the Mac you are using.
External hardware (e.g. audio interface, drum machine, MIDI controller)...?
When does this message appear? On new projects? A specific project? Upon opening a project...when attempting to save a project?
Have you changed or installed anything recently?
In the meantime try deleting Logic's preferences (after quitting Logic):
Go to users/Library/Preferences/
& delete the following file:
& restart Logic.
Also try repairing permissions on your Mac:
I'd also ask you to consider either adding your system spec to your profile here:
or typing it into a post.