Comment 11 for bug 1166765

> gsettings reset org.compiz.core:/org/compiz/profiles/unity/plugins/core/ active-plugins

Yep, this did the trick. Turns out that "compiz (core) - Error: Plugin 'opengl' not loaded." means "opengl was not loaded and you need to fix this" and not "opengl was not loaded because of an error."

Thank you!