At last I solved the problem with version.h: "make-kpkg kernel-image" does a "make clean" so version.h gets deleted. I just saved it before and copied it back. The driver can be complied then.
Now I have another problem, but that seems to be one with 2.6.5: depmod: QM:MODULES: Function not implemented
Ok, you have to install module-init-tools, then it works. And voila: the module gets loaded and I have X running.