I use Knoppix 3.6 installed onto my hard drive, so it's basically a Debian distro. I have upgraded it to KDE 3.3.1-2, but I am now having problems with compiling KDE programs (specifically, superkaramba 0.35).

The error I get when I ./configure is:

[snip configure output]
checking for KDE... configure: error:
in the prefix, you've chosen, are no KDE headers installed. This will fail.
So, check this please and use another prefix!

Now when I go into aptitude and try to install kde-devel, it lists 3 broken packages:

kdelibs4-dev
libkonq4-dev
kdebase-dev

kde-devel is at version 5:42, but all 3 packages seem to be at 4:3.2.2-1. When I try to upgrade these 3 packages, they conflict with my existing libraries because they are of different versions.

I have tried to upgrade my package lists, but they have been fully upgraded and the same error occurs. However, when I check on debian.org, those 3 packages DO have new versions for KDE 3.3.1. It appears that aptitude is not downloading the complete updated package lists.

I did modify my sources.list by replacing the default German sites with US ones, but this shouldn't cause a problem, should it? Debian.org has downloads for the updated packages available on the US servers, and while I could download them all one by one and install them manually, I would rather get to the root of this problem.

I also removed some sources from ftp.gwdg.de because they were returning Not Found errors in aptitude (only recently; they worked before). However the comments in sources.list indicate that they are only for Java packages.

Any suggestions?

deb ftp://linux.csua.berkeley.edu/debian testing main contrib non-free

you should add a line kinda like this and try running apt-get update.
or... i dunno about what debian version knoppix is based on, but I would probably just upgrade everything to unstable. What it sounds like is version problems... Try changing your sources.list to unstable, then running apt-get update, then apt-get upgrade.

Honestly, I would reccommend installing pure debian rather than fiddling with knoppix.

Yes, it appears I forgot to set the default release to "unstable" so aptitude was still using the testing packages. Thanks for pointing that out.

Regarding Knoppix, I happen to like it since it's a very complete and ready-to-run distribution. When I installed it a few months ago I was still pretty new to Linux, so it was a good introductory distribution. In the future I'll probably try a fresh Debian install.