Caution:
Well, it would appear that I'm a hopeless newbie because I simply don't understand what's going wrong here:
First strange thing is i cannot seem to su to root while I'm logged in as another user. 'su' asks me for the password but claims it to be invalid after I enter it. Same with 'su root'. I remember having used this to gain root privileges without any problem on another machine! What am I missing?
Second thing seems to be related to the first. I have to set UID a program (namely aterm) to be able to start it as another user. So I did a chmod 7755 aterm, which changed the permissions to
-rwsr-sr-x 1 root root
According to my knowledge this should give any user who starts the program root privileges, in effect allowing every user to start it. However when I try to launch it as another user, it still tells me that it "has to be installed suid root".
These two features are essential as I cannot use my system effectively as another user than root without them (and I'm sure everyone is gonna tell the whole story again about how bad this is

).
Is my root account somehow broken? Or is it something else? I'm left completely without a clue...
Thanks for any feedback!