Kernel 2.6.21 (including) and up: the kernel module fglrx.ko will not be built ... and the ATI installer wont tell you, it has not.
ATI kernel module has non-GPL License. Kernel build system has restricted the usage of some functions to GPL-only modules. So the kernel module won't be compile.
a) Go kick ATI to buld a GPL compatible kernel module.
b) Modify the MODULE_LICENSE String in the kernel module to "GPL"
Dr. Nikolaus Klepp