i customed kernel 2.6.10 downloaded from www.kernel.org
and it works well.
but working with the new kernel, my fglrx drivers can't work anymore.
i have recompiled fglrx under new kernel, however problem remained.
maybe fglrx failed to support by kernel 2.6.10?
it works well under 2.4.20-8 ( kernel for redhat 9 )
my distribution is redhat 9 with ati 9550 graphics card.