It's because you're using a very recent kernel. Quick workaround:
http://idratherhack.blogspot.com/2011/04/nvidia-drivers-fail-without-
smplockh.html
** Changed in: fglrx-installer (Ubuntu)
Status: New => Confirmed
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https://bugs.launchpad.net/bugs/776895
Title:
package fglrx 2:8.840-0ubuntu4 failed to install/upgrade: fglrx kernel
module failed to build
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