Have you tried updating OSX to make sure you have all relevant updates?
The error code listing on Mylenium's site would indicate that checking your system for updates may be a good path to pursue.
If you've done so, and the problem persists, you could disable OpenGL by temporarily moving the plugin outside of the plug-ins folder.
Also, what effects are you using in your project? Perhaps one of them may be causing your woes?
I don't think updating the Mac OS will help with this (it won't hurt either, of course).
I don't think moving the OpenGL plug-in is necessary either.
In fact, a very likely reason why you're seeing this error message is because the OpenGL plug-in was probably moved manually from the specific folder it should be in, to the root of the Plug-ins folder or the AE folder itself, and then an updated copy got installed in the original location.
Try to see if this is the case, the OpenGL plug-in is called AE_OpenGL.plugin, and it should reside in Plug-ins/Extensions. If there's a duplicate hanging around in the Plug-ins folder or the main After Effects folder, it may be the culprit. Just delete that duplicate.
I agree, a duplicate could considerably throw things off traack and effectively disable all OpenGL. You're even lucky that it doesn't crash the program right away. I'd definitely check if indeed you have multiple versions stil lfloating around. If that isn't the case, It's possible that some update didn't go right and anotehr component such as DynamicLink or Mediacore is affected. This can happen when you are in a suite (Master Collection etc.) or use e.g. Premiere and Encore, also. Letting the apps check for updates and running the Adobe Updater may fix the problem as well...