Ever since I switched from 2.79RC to 2.79a, I’ve been experiencing this weird behavior.
Select “Cycles” from the drop-down at the top of the screen.
Press F12 or “Render” button.
Render completes as expected using Cycles.
“Blender Internal” becomes selected automatically.
Is there some reason it’s doing this, or does it seem like a bug to you? It’s only mildly annoying, but annoying nonetheless.
Edit: Appears to be a problem with the Crowdrender add-on.