Ok, given no one yet answered I went on with tes and finally woked it out somehow. I used a pack extractor by Verci and somehow i was able to unpack the two skeleton.dat files and repacke their contesnts into one sekelton.dat

No more skeleton message errors, hurra!
But.. well.. now animations are the problem.

I tried the same procedure and the first pack.dat unpacked succesfully, but the second one does not. The unpacker says: "not a valid idx archive" or something like that and stops.

I tried leaving the animations of the first pack unpacked and using the pack.dat of the second in animation folder, but the game CTD without even a error message :(

So now I'm wondering if there is someone around SO NICE to try to unpack that pack.dat - pack.idx file for me