I am using the latest Ubuntu OS and up-to-date Chrome browser. Occasionally when I am working at a 5 hour stretch, the computer will freeze up completely and I will have to close down manually and reboot. When this happens I lose the material I have been working on as I cannot save it. And I often receive a notice at this time saying that my profile is not available or that I do not have a profile. I am an Ubuntu user not a technician and do not know what to do about this problem.