Since the build of org mode of the end of august (now I use elpa/org-20150907), the M-RET does not start a new entry, and gives the error "Symbol's value as variable is void: org-planning-line-re". Strangely enough, M-SHIFT-RET still gives a new TODO entry.
I am currently on aquamacs emacs on OSX El Capitan public beta, but I do not think it is a system issue. In fact, if I go back to the aquamacs-bundled version of org (8.2.10, I do not know of which date, but I presume late 2014) M-RET works again perfectly.
Is anyone else having the same issue?