Alkis Mavridis, what you have described seems to be an X freeze. It could be caused by any number of things, and you need to take some additional steps to provide a complete report.
When did you upgrade to this version of Ubuntu? When did you first notice the freezes occurring? How frequently do the freezes occur? How many per day would you say you experience? List the applications you typically have open at the time of the freeze. Think back to the last few times it froze. What activities were you doing in each of those times? Do you have compiz enabled? Does the issue go away if you disable it? If your system is a laptop, do you suspend/resume it? Had you resumed at some point prior to the freezes? Please attach all relevant information noted in: https://wiki.ubuntu.com/X/Troubleshooting/Freeze Finally, and most importantly, please collect a GPU dump after reproducing the bug. Packages to install and directions for doing this are available at: https://wiki.ubuntu.com/X/Troubleshooting/Freeze#How%20to%20Get%20a%20Batchbuffer%20Dump%20(-intel%20only) With the GPU dump in hand, we will be able to upstream this bug. ** Package changed: linux (Ubuntu) => xorg (Ubuntu) ** Summary changed: - Kernel Oops - Computer crashes when I click on the network icon. + Computer freezes when I click on the network icon. -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xorg in Ubuntu. https://bugs.launchpad.net/bugs/954858 Title: Computer freezes when I click on the network icon. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/954858/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp