I hate the breakage in the open source drivers. You know what I mean: the artifacts, flashing, white lines everywhere, etc. The latest open source git drivers seem to have a lot of this fixed. While I'm sure you can wait until the next release when we get newer drivers, here is how to do this in Jaunty and get your system fixed now. Worst case scenario of doing this is that on your particular card all the cleanup hasn't been done yet, but on my x1200 this worked wonderfully.

Open up a terminal and do the following:

sudo apt-get install build-essential autoconf automake libtool pkg-config git-core

sudo apt-get install libdrm-dev x11proto-gl-dev mesa-common-dev xutils-dev x11proto-xf86dri-dev x11proto-fonts-dev x11proto-randr-dev x11proto-video-dev x11proto-xext-dev x11proto-xinerama-dev x11proto-render-dev xserver-xorg-dev

git clone git://anongit.freedesktop.org/xorg/driver/xf86-video-ati

cd xf86-video-ati

sudo ./autogen.sh --prefix=/usr --enable-dri

sudo make

sudo make install
Now restart your machine and you're using the new drivers. Try bumping up your visual effects to max and see what happens. If you're lucky like me, everything will work flawlessly. If not, then you may want to wait a couple weeks and try it again, but you're no worse off then you were before.