I have been unable to restart, shutdown, or log out of ubuntu since the release of 12.04. I have upgrade at the time of release for 12.10 and now for 13.04 and have had no change in the situation. On logout or restart i get a solid black screen where it just sits.
I have let it sit for long periods and I get a message every 2 minutes or so stating something about Xorg blocked for 120seconds. I have search extensively and can't find anything that actually fixes it. Using the shutdown now command works from terminal with -P -r. Updating grub had no effect. Any clues or help would be great.