Installing Red Hat Linux 6.1 + updates on a system whose motherboard has an on-board SiS 5597/5598 video controller, the fonts in X are solid blocks of colour. After much tweaking a working fix was found to be to add to the /etc/X11/XF86Config file in the video card section: Options "xaa_no_color_exp" Apparently this video hardware worked fine in XFree86-3.3.3.1 and got broken since then...
*** This bug has been marked as a duplicate of 6970 ***