can't save search box configuration under themes>config
I had the same problem - answer: Search module is not enabled by default! So 


go to admin/build/modules, scroll down to 'Search' and tick the checkbox.
Then go to admin/user/permissions, scroll down to 'Search module' and set permissions for Anonymous and authenticated user (and any other type of users you might have configured and want to give this permission to).
Finally, go over to admin/build/themes/settings/[your-theme-name] where you will find that the 'Search box' checkbox is now tickable.


You should now see the search box - if you don't , flush caches!