Back on 13.04 it didn't occurred. I've upgraded to 13.10, systems apparently working fine, but, when I put it to sleep(using or not using extended monitor) and try to wake up, I see the screen(both), without lock-screen, but completely freeze, Neither tty open, nor the keyboard works. So, only option remains is to force shut-down. Any clue how to investigate the cause or fix it? Thanks in advance, any info that'll help you could ask! Ubuntu 13.10 x64 - not a fresh install/upgraded - with Unity Dell Vostro 3550 AMD Proprietary Drivers - 13.11 / Hybrid with Intel