An update: the solution suggested on comment #3 at the link http://www.linuxquestions.org/questions/slackware-14/lags-and-freezes-on-ati-rs880-%5Bradeon-hd-4290%5D-with-new-xf86-video-ati-7-8-0-a-4175594206/
did solve the problem for me. I did some more investigation and found out that what did the trick was forcing the radeon driver to use DRI3. However, this solution created another problem: when I resize the window of a GTK application, my desktop goes crazy with all sorts of weird artifacts, with the windows flashing, etc. Going back to DRI2 solves the problem, but then I go back to the original one, with the plasma desktop freezing at random times (though I can fix that by switching to a virtual terminal and then going back to the graphical desktop). Anybody else still having this problem? Thank you, Adriano
