It seems to be related to the last xorg-x11-server (184.108.40.206-3.fc7). You can try to revert to the previous version -220.127.116.115- (considering the dependencies involved, you may not have to revert other rpms to their previous stage).
To do so:
1- boot in runlevel 3 (add 3 at the end of the kernel line -> when grub starts, press e key to get in edit mode, position at the end of the line, add 3, enter and boot)
2- download previous rpm using wget
$ su -
$ password: <root password>
# wget ftp://ftp.uni-bayreuth.de/pub/redhat.com/fedora/linux/core/development/i386/os/Fedora/xorg-x11-server-Xorg-18.104.22.1685-5.fc7.i386.rpm
3- install it to replace the new rpm:
rpm -i xorg-x11-server-Xorg --force
In case of trouble, boot one more time on runlevel 3 and just type (with root rights):
You will then restore the last situation.
Anyway, do fill a bugzilla...