Apple just released Mac OS X Lion 10.7.4 today, May 10, 2012.
The OpenCL compiler in 10.7.4 has changed resulting in the failure to render on ATI GPUs with the GPU accelerated OpenCL renderer in version 2.2.0 of Fractal Architect 2. (OpenCL CPU based rendering is unaffected.)
There is a bug fix release of Fractal Architect (version 2.2.1) that is still in Apple’s review queue. Hopefully it will be released on the Mac App store soon.