I thought I should flag up this bug report here: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=29329
The basic problem being, org-gnus.el uses a bunch of Gnus macros, but doesn't require the relevant Gnus libraries when compiling. BUT! No error is raised when compiling Org using "make", so there must be more going on than that. I know I've seen these errors in the past, but only briefly, which makes me thing it was a temporary version mismatch between Emacs and Org, or something like that. Anyway, I figured someone here ought to be able to shed light on this. Eric