MikeTaylor
Since you are on ATI, it's not likely a display driver problem. Make sure that you have X11 installed on your machine. It's an optional install on OS X. The program that we use to convert out SVG icons has a dependency on X11.
If you don't have it installed, you should be able to install it from your OS X install DVD.
So after install X11, Houdini works well ! Icon is present and no openGL lag !
I don't create a big scene yet. Any way, I want only use Houdini at home on my iMac to practice it, if I'm not using it at work (some time I need to work on Maya).
Thanks for your help !