I don't know if this will help - The "barrier based sync failed on dm-0:8" is I think a symptom of something else.
Today, I experienced the same, and "solved" it:
Everything was running fine w/ kernels: 2.6.29.4-167.fc11.x86_64 2.6.29.5-191.fc11.x86_64
Today, updates included a new kernel: 2.6.29.6-213.fc11.x86_64
On reboot, the JBD message came; I tried the previous kernel and boot was fine.
I looked through the yum logs, saw a kernel update had happened.
If you have a non-standard video driver in your system install (before you tried this kernel) you may be experiencing the same symptom I did.
Your choices are to restore the default video driver in /etc/X11/xorg.conf, or re-install the optional video driver.
I use NVIDIA's graphics driver (dual-headed). For the 64 bit kernel (at least), with each Fedora Kernel update I have to "re-install" (well, probably just re-compile the kernel interface to the nvidia driver, but I let it do all it's default things anyway).
To accomplish this, I change to init 3, run the nvidea driver installer, and reboot. If you can't boot, you can bootsrap from a live CD, and change your /etc/inittab (to init 3), and then boot from the kernel of interst. Since this is a bit of a pain, I've also changed /boot/grub/grub.conf (commenting out hiddenmenu).
You can see more comments about this on 2linices.blogspot.com
Regards, Yarko