I am running the U6 and this happened in older version as well, I think the two things may not be relayed just a problem of handling system resource, I find sometimes some apps will auto close when wake up from screen saver. I ran Firefox and Thunderbird with only a static screen, I left the PC unattended for an hour or so, when I come back to re-use it I find the running apps disappeared, but this may not happen next time wonder why.
excluding firefox, and other browsers. which program(s)?
I only have this problem with Firefox and Thunderbird for now, not sure about others and that not happen every time.
firefox has a memory leak, and i’m guessing you only have 8G of memory
# swapinfo John firstname.lastname@example.org