I've just installed ubuntu 16.04 lts and few applications. For some unknown reason my pc freezes. Sometimes when i log in into my social network account through chromium, sometimes when i open video file, sometime when i run application. So when i do something (open/load etc.) there is a chance that my pc freeze. When it "freezes" screen becomes blank brown or black colored. How can i find the reason of all this? Does ubuntu have any logs that capture this? P.S. i've cheched ram several times with memtest86+, checked my hdd (i have 120Gb SSD for ubuntu). I didn't install any non standart drivers or so on.