I've upgraded much of my system including kde to kde 3.4 and now I'm getting these 2 problems -
1. I use kppp to connect to the internet but since I upgraded at the point it actually connects, it restarts X, exactly as though I have done alt-ctrl-backspace. This happens when using kppp in kde, gnome or xfce4.2
2. I am now having problems when running programs as root, here are some examples -
In kcontrol when I try to change to administrator mode to change the login settings I get the error "SU returned an error" if I try using gksu to run kcontrol as root, the window appears then disappears again.
If I launch konqueror as root and try clicking on /usr/bin/kcontrol nothing happens.
When I try to edit a text file as root in konqueror I get "could not launch kdeinit" or "kdeinit could not launch kwrite" or something to that effect (sorry, I'm not at home at the moment to check the exact message).
It's not all related to trying to launch kcontrol or konqueror but some other programs such as synaptic, guarddog and even nautilus super-user moderun as root perfectly fine.
It seems the problem is only affecting kde apps whether I run them in kde, gnome or xfce4.2
Someone please help me.

what distro?

I am running into strange things with sarge, and I wonder how much of it is because I chose sarge instead of woody.

I do love my debian machine, though. I want to get it working and bug-free.

I meant to add this info at the bottom of my post but somehow forgot.
I'm using debian sid/unstable and I used the ubuntu repostiories to install kde3.4, gnome 2.10 and X.org.

Although I'm not having any problems at all with gnome or X.org, I've noticed a few other niggling problems with kde other than the ones I mentioned in the first post so I'm going to completely remove all traces of kde and go back to version 3.3 since I still have all the old packages in cache. Hopefully that will solve my problems.

Well, you've been playing with fire and got burn.
This is uncharted teritory and I am afraid that you should have been aware that staility problems might come up.
I don't want to be an I-told-you-so-guy, but you might try to pin back to debian's unstable.

Hint: read apt-pinnning tutorials and force priority over 1000. FIRST READ THE TUTORIAL AND UNDERSTAND WHAT PRIORITY 1000 MEANS!

Firstly, I'm still very much a beginner and so I don't keep anything of major importance on my linux yet so I don't see that I have much to lose by experimenting. Also, the more cock-ups I make the more I'm learning about linux, if everything always went smooth I wouldn't learn anything
Secondly, despite what I've just said, I did do plenty of reading up and checked a couple of guides on using ubuntu packages on debian sid/unstable as well as how to avoid updating problems etc.

As it turns out, while checking I had the right packages installed, I noticed I had installed the kubuntu-default-settings, I removed that and now everything appears to be working properly.