I'm running Fedora 9 with no problems for over a month now and have only had to reboot a few times after kernel updates and what not. After upgrading from 2.6.26.6-79.fc9.i686 to 2.6.27.5-37.fc9.i686 on my dv6809wm laptop, the boot process hangs at udev. However, this only happens if it is unplugged and if I plug it in once it hits this point the process resumes. I have tried some things recommended elsewhere with no luck. These include:
disabling rhgb
removing the wireless driver
When I boot the 2.6.26.6-76 kernel it load fine. The other notable problem is, when resuming from suspend with either kernel I only get a blank screen. It doesn't help to switch virtual terminals. If I boot the old kernel into init 3 then suspend and resume the system does respond to pushing the power button by shutting down.
Edit/Delete Message

OK, I ended up just downgrading to a more familiar experience. Just kidding. I did a yum remove kernel-2.6.27.5-37.fc9.i686 and then rebooted to the previous kernel and reinstalled my drivers. Everything works great. I'll just have to wait til this is fixed. It seems like there are a couple other folks with the same problem. I hope this helps.