Well it only happens when changing system settings, so as she doesn't play with them usually everything is fine, the system runs flawlessly.
But I ran into this bug on my laptop last week and thought somethings buggy with my installation, but obviously it isn't, it must have to do with something else. After Ctrl-Alt-Backspace and re-login Synaptic won't start from the menu (on both machines), but after reboot everything's fine until I try to apply changes in system settings.
I have disabled some options in the desktop effects after upgrade to 4.5.2 as there are known problems with Intel onboard graphics.
I'll try some more workarounds though:
1. disable desktop effects completely
2. if 1. is a success, enable / change options in desktop settings to see if I can find the culprit
3. try the pae-kernel
Just thought someone had the same issue as it seems to be a bug.