I had the problem yesterday. I started Gaea after a long time, I clicked the internal update… from .0 to .8 I think? And then it didn't work anymore. So I downloaded it from the page … which is at .7 currently. And that fixed it.
No idea which version it was actually installing from inside Gaea, but that bugged out completely.
EDIT: I think I had a "bleeding edge" version installed before and then it updated with the regular version? Maybe that doesn't work.