"When you click on a .src.rpm or a.rpm file all you get is the package manager window with three tags, Description, Changelog & Files I have no Install button any more."
I would guess that YaST2 has become corrupted somehow. I would first reinstall YaST2 using command line rpm. First list all of the packages you have installed with:
rpm -qa > /root/all.rpm.txt
Then look through /root/all.rpm.txt for all of the YaST2 package names. You can install these packages from the SuSE CD using command line rpm or kpackage.
Personally I use rpm and kpackage to install rpms, never YaST2. I go into kcontrol and set *.rpm files to be opened by kpackage when I click on them. I install from the command line using rpm. You could use rpm and kpackage to get yaST2 working again or you could use them permanently.
Be prepared. Create a LifeBoat CD.