I'm running Debian Sid.
I installed Sarge, then dis-upgraded to Sid.
But, it seems that Firefox/Mozilla/Real Player etc. can't locate the gtk correctly, since they have the rectangle simple look, not the usual GTK round buttons. Starting either one in konsole, doesn't give any erros, like my firefox did on SuSe when I upgraded my gtk.
gtk2 is installed, running newest version as present in Sid repositories.

have you tried installing the libgtk2.0-common package?

The file is installed.

Since Gnome works fine (I usually use KDE) I believe that the problem is just a setting being different to my other linux, SuSe. The thing im looking for is more a extension of the desktop theme, keramik, to other Programs. If firefox had trobule finding it, it would give verbose output in console, and I'm sure I would have more problems then just a different look if my gtk libaries were missing.

I would say try apt-cache search gtk theme and take a look at the packages there to see if any are installed. If you want the kerimak look I believe it would be gtk2-geramik or something like that for the name that you need to install to get the theme close to matching or you can install the gtk2-qt theme to apply it to the apps to get a unified feel this is most likely the one you are missing. If you are using KDE most of the time then there is the option to apply the colors you are using to non-kde apps in the Appearence & Themes -> Color option in the Control Center as well.

Thanks a lot!

After unstalling a bunch of gtk-qt packages I had the option of using my GTK style in KDE apps under the KDE CC.