I'm currently working from a Windows 7 system (Sony Vaio VPCEB1Z0E) with an ATI GPU. I've installed Fedora 16 as a virtual machine using VirtualBox v4.1.10, everything was fine so I did a 'yum update' and then installed the packages required to install the Guest Additions:
kernel-devel kernel-headers dkms gcc gcc-c++
and then installed Guest Additions in the usual manner.
I'd seen a few posts about problems with SELinux and the VirtualBox Guest Additions so before rebooting I ran:
restorecon -R -v /opt
After the virtual machine rebooted I found that Gnome is upside down and on logging in I'm witnessing all kinds of weird behaviour.