Please post the sub revision level of the kernels you are using and your kernel boot parameters. Can you get any error messages in the kernel logs?
As I stated before, the problems are present with all 2.6.6-X kernels officially released on fedora channels. I tried every subversion released. No problems with 2.6.5-X, all subversions.
My boot parameters (I include som lines from my grub.conf file):
title Fedora Core (2.6.5-1.358)
kernel /vmlinuz-2.6.5-1.358 ro root=/dev/vg00/lvol0 rhgb quiet vga=791
title Fedora Core (2.6.6-1.435)
kernel /vmlinuz-2.6.6-1.435 ro root=/dev/vg00/lvol0 rhgb acpi=off vga=791
Note the acpi=off option, essential for me, to boot with any 2.6.6-X kernel without freeze.
I carefully examined kernel logs after freezing, but I didn't see any unusual string. Maybe there wasn't enough time for syslog to write errors before freezing?