It sounds like you have both (incompatible) drivers in your xorg.conf. You can have as many screen sections, or videocard sections as you like, and xorg will use what it finds.Take out the section(s) with your oss driver. If you're not going to use it, why keep it?
The proprietary driver uses it's own libs like libGL.so which means you only can have one or the other. Try this
ls -l /usr/lib/libGL*
ls -l /usr/lib64/libGL*
and you'll probably see what I mean. On my nvidia box, I libGL.so --> libGL.so.1 --> libGL.so.96.43.14 which is the old driver for cards made when nvidia was still operating out of someone's garage
. Don't have the fglrx driver handy any more; not since it messed up my system when the script went mad as root.When you uninstall the fglrx driver, it puts the old libs back, or tries to.