Ok, now i'm quite confused..earlier today as i looked for the file in that directory it wasn't shown.
As i now tried to get xfee, it doesn't find the package (also made an apt-get update before), so i also wasn't able to remove it either.
Now, though, i found libX11.so.6 in /usr/X11R6/lib (somewhat stupefied me, for i'm sure it wasn't there before), but the same problem still occurs while trying to load gdm
also tried apt-get install xlibs --reinstall, as someone recommended, but it didn't seem to help there either