Rumors of serious conflict...

Unsourced rumors, to be precise.

And multiple unnamed sources might well all originate from one source, so the "multiple" adds no weight if the pedigree of the information is so low.

If O'Keefe was still NASA director I wouldn't doubt it for a second, but Griffin seemed to be somewhat more pragmatic, especially given the strong political pressure he must have been under for the last few years.

But... well, read the Orlando Sentinel article ("NASA has become a transition problem for Obama") yourself.