I have just upgraded (?) from LR6 to CC, when I try to open LR it tells me " The LR catalog named Lightroom catalog cannot be opened because another application already has it opened. Quit the other copy of lightroom before launch". I do NOT have the old LR6 open, I have even made sure it is uninstalled, have restarted my computer several times but still get this message. I really do not want to start another catalog by importing 50000 photos and then keywording them !
FWIW, using windows 10 with latest update.