Restart the server locally, and watch the output screens, to see where the problem exists.
If it's a kernel update problem then you can select an older kernel from the boot sequence and get back up and running, at which time you should edit your bootloader to go back to using the old kernel.
If it's a firewall problem, then you should be able to log in locally and set the firewall so it won't restart automatically at the next boot. Then fix the firewall before re-enable it.
Jeff