[dm6257]

I had the same problem when I followed the directions you referenced. When I installed kernel-source and kernel-syms using the YaST package selection GUI.( I selected Patterns at the bottom, found Linux Kernel Development and selected kernel-source and kernel-syms and installed them.) When I executed ./VBoxLinuxAdditions.run as root, it worked. I also couldn't install just the headers as I did with Ubuntu and had to load the entire 254Mb package. But all's well...