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[David W. Aquilina]

As you've become aware, there are different variants of the kernel. One for systems with one processor that can address up to 4G of memory, an SMP variant for multiple processor systems that can address up to 16G of memory, etc. The development headers are specific to which variant of the kernel you're running. If you look at which kernel packages you have ('rpm -qa | grep kernel'), you''ll probably see multiple entries. One will probably be 'kernel', another should be 'kernel-smp'. The kernel-devel and kernel-smp-devel packages correspond to these packages. 

If you booted into the UP kernel, the kernel-devel package that you installed would have worked just fine. 

-- 
David W. Aquilina
david at starkindler.us