Ubuntu on my laptop has frozen multiple times in last 6-7 months. Its not frequent but I can not relate the freezing to anything which I was doing. Today it froze again when I was taking notes in class - approximately at 12:00 PM. During the freeze both mouse and keyboard stopped working. I tried Alt-Ctrl-F1, Alt-Ctrl-F2 etc without any success. After that I waited few minutes & then I restarted the laptop. I checked /var/log/syslog and /var/log/kern.log and it seems that it did not log anything (I was not able to understand most of it). Please let me know if you can find something unusual at around 12:00 PM. Is there any other log which might be useful? Here are the /var/log/syslog and /var/log/kern.log files.