Description of problem:
On my laptop that I have just upgraded to F16 (from F15, using preupgrade), X crashes when attempting to display the GDM screen, displaying the 'oops, something has gone wrong' screen. I can boot and log in to gnome when I specify nomodeset as a kernel boot parameter. This all worked fine under F15

Version-Release number of selected component (if applicable):
kernel-3.1.0-7.fc16.x86_64
xorg-x11-drv-ati-6.14.2-2.20110727git8c9266ed2.fc16.x86_64
xorg-x11-server-Xorg-1.11.2-3.fc16.x86_64

How reproducible:
Every time

Steps to Reproduce:
1. Boot laptop
2. Watch the 'oops something has gone wrong' fail whale come into view
3.
  
Actual results:
X crashes

Expected results:
X doesnt crash

Additional info:
The graphics card is a Radeon HD5450. Running lspci -v gives

01:00.0 VGA compatible controller: ATI Technologies Inc Madison [AMD Radeon HD 5000M Series] (prog-if 00 [VGA controller])
	Subsystem: Sony Corporation Device 9071
	Flags: bus master, fast devsel, latency 0, IRQ 16
	Memory at e0000000 (64-bit, prefetchable) [size=256M]
	Memory at f0020000 (64-bit, non-prefetchable) [size=128K]
	I/O ports at d000 [size=256]
	Expansion ROM at f0000000 [disabled] [size=128K]
	Capabilities: [50] Power Management version 3
	Capabilities: [58] Express Legacy Endpoint, MSI 00
	Capabilities: [a0] MSI: Enable- Count=1/1 Maskable- 64bit+
	Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1 Len=010 <?>
	Kernel modules: radeon