Totem's web browser plugin (in 3.2 and later), fail to work correctly with WebKitGTK+ applications.
Clutter-CRITICAL **: Unable to initialize Clutter: Unable to find suitable fbconfig for the GLX context: Unable to find fbconfig with rgba visual
Using Clutter in a plugin seems like a bad idea, in general, because Clutter is known to interact badly with other users of OpenGL in the same process. Perhaps that particular issue can be solved by out-of-process plugins (coming in WebKit2).
That said, I'm not sure why it's failing to get an appropriate visual. Is it possible to get a stack trace (even one without line numbers) at the point that the critical warning is printed?
Totem's web browser plugin doesn't exist any more.