As the 'Guidance Power Manager' applet only works if you have a battery, I installed "kpowersave" which does also allow suspend to RAM. If I set the screen locking to "auto" or "KScreensaver" then the session returns unlocked. If I set it to "xlock" (and the package 'xlockmore' is installed), then upon resume the session is locked with xlock. So this is some kind of workaround.
As the 'Guidance Power Manager' applet only works if you have a battery, I installed "kpowersave" which does also allow suspend to RAM. If I set the screen locking to "auto" or "KScreensaver" then the session returns unlocked. If I set it to "xlock" (and the package 'xlockmore' is installed), then upon resume the session is locked with xlock. So this is some kind of workaround.