When launching startx, I first have an error message: _X11TransSocketUNIXconnect : can't connect - errno 111 and then, the Xserver (XF86_SVGA) is correctly started. If I replace xinit (from rpm XFree86-3.3.3.1-52), by xinit from the official distribution of XFree86-3.3.3.1, then, the "bug" is fixed. My video card is a Matrox Millenium MGA (2MB or ram).
This issue has been forwarded to a developer for further action.
this will be fixed in a forthcoming errata release of X.