The following was filed automatically by setroubleshoot:

Summary:

SELinux is preventing Xorg "read write" access to device vga_arbiter.

Detailed Description:

[Xorg has a permissive type (xserver_t). This access was not denied.]

SELinux has denied Xorg "read write" access to device vga_arbiter. vga_arbiter
is mislabeled, this device has the default label of the /dev directory, which
should not happen. All Character and/or Block Devices should have a label. You
can attempt to change the label of the file using restorecon -v 'vga_arbiter'.
If this device remains labeled device_t, then this is a bug in SELinux policy.
Please file a bug report (http://bugzilla.redhat.com/bugzilla/enter_bug.cgi)
against the selinux-policy package. If you look at the other similar devices
labels, ls -lZ /dev/SIMILAR, and find a type that would work for vga_arbiter,
you can use chcon -t SIMILAR_TYPE 'vga_arbiter', If this fixes the problem, you
can make this permanent by executing semanage fcontext -a -t SIMILAR_TYPE
'vga_arbiter' If the restorecon changes the context, this indicates that the
application that created the device, created it without using SELinux APIs. If
you can figure out which application created the device, please file a bug
report (http://bugzilla.redhat.com/bugzilla/enter_bug.cgi) against this
application.

Allowing Access:

Attempt restorecon -v 'vga_arbiter' or chcon -t SIMILAR_TYPE 'vga_arbiter'

Additional Information:

Source Context                system_u:system_r:xserver_t:s0-s0:c0.c1023
Target Context                system_u:object_r:device_t:s0
Target Objects                vga_arbiter [ chr_file ]
Source                        Xorg
Source Path                   /usr/bin/Xorg
Port                          <Unknown>
Host                          (removed)
Source RPM Packages           xorg-x11-server-Xorg-1.6.99-43.20090828.fc12
Target RPM Packages           
Policy RPM                    selinux-policy-3.6.30-1.fc12
Selinux Enabled               True
Policy Type                   targeted
MLS Enabled                   True
Enforcing Mode                Enforcing
Plugin Name                   device
Host Name                     (removed)
Platform                      Linux (removed) 2.6.31-0.190.rc8.fc12.i686 #1
                              SMP Fri Aug 28 19:07:13 EDT 2009 i686 i686
Alert Count                   2
First Seen                    Wed 02 Sep 2009 03:58:58 PM CEST
Last Seen                     Wed 02 Sep 2009 03:58:58 PM CEST
Local ID                      9021cd33-4262-4abd-a951-6d9d4c541c7a
Line Numbers                  

Raw Audit Messages            

node=(removed) type=AVC msg=audit(1251899938.609:100): avc:  denied  { read write } for  pid=17275 comm="Xorg" name="vga_arbiter" dev=tmpfs ino=3531 scontext=system_u:system_r:xserver_t:s0-s0:c0.c1023 tcontext=system_u:object_r:device_t:s0 tclass=chr_file

node=(removed) type=AVC msg=audit(1251899938.609:100): avc:  denied  { open } for  pid=17275 comm="Xorg" name="vga_arbiter" dev=tmpfs ino=3531 scontext=system_u:system_r:xserver_t:s0-s0:c0.c1023 tcontext=system_u:object_r:device_t:s0 tclass=chr_file

node=(removed) type=SYSCALL msg=audit(1251899938.609:100): arch=40000003 syscall=5 success=yes exit=8 a0=80fdf7 a1=2 a2=b12ef0 a3=811240 items=0 ppid=17274 pid=17275 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=tty7 ses=4294967295 comm="Xorg" exe="/usr/bin/Xorg" subj=system_u:system_r:xserver_t:s0-s0:c0.c1023 key=(null)


audit2allow suggests:

#============= xserver_t ==============
allow xserver_t device_t:chr_file { read write open };