I am working with Ubuntu 12.04 for a while now, constantly upgrading and afterwards cleaning with Ubuntu-Tweak's Janitor. Everthing went fine until about two weeks ago: then my computer constantly froze after approx. twenty seconds. Sometimes I had an error message, but not always, saying:
Nothing helped, the problem continued. I re-installed. Then it worked again, I updated, but did not use Ubuntu Tweak. It worked, today (march 19th) I updated only and had the problem again. Recovery mode does not help.
What to do?