I've exported the texture again, changed the file in the skin editor and now it is placed right. You're right. Probably the file was broken. Thank you!

Gamestudio: A7.82 Commercial/A8 Commercial
System specs (Laptop):
Windows 7 64bit
DirectX v10.1
Intel Core i7-720QM CPU @ 1,60 GHz
4GB DDR2 Ram
NVIDIA GeForce GT 230M (1024MB)