Okay so it happened again while I was trying to write this.
I don't know if this only happens in KDE, but I haven't tested in other interfaces.
Sometimes pressing Ctrl+Z to undo twice in Blender doesn't undo. Instead it causes your session to immediately terminate. Under certain conditions, using Extrude Region yields the same result. This is what I will show how to reproduce.
I'm using Granular Funworks 2007.
how to reproduce:
(to avoid confusion, I say 'hit' for buttons on the keyboard and 'push' or 'click' for on-screen buttons)
1) open Blender in KDE (doesn't matter which one - DRI disabled, FullScreen, normal, wutev.)
2) hit Tab. gray square in the middle turns pink with yellow border.
3) in the toolbar just below the section with the pink square in it, push the second to last button that has a little picture of a cube in it.
4) move your cursor into the dark gray gridded region with the square in the middle and hit the A key. the square turns blue with black outline, pink corners.
5) hold Ctrl and the left mouse button and drag around the blue square until the dotted line surrounds it. it should turn pink with yellow outlines again.
6) hit 1 on the number pad (NOT the 1 key above Tab and Q. on my laptop, this requires me to hold Fn while hitting the J key). the square turns blue agan, but now the outline is yellow on top and black with pink corners on bottom.
7) make sure your cursor is still somewhere in the dark gray gridded region. Now hit the E key and select Region in the Extrude menu that pops up. It should already be highlighted, so click it and watch what happens. If it's the same as what happens to me, your session will immediately and abruptly terminate and you will return to the logon screen.