I wish I could be more helpful, but had a hard time getting 11.6 installed properly after having ubuntu installed ATI drivers.
However, if you go to the AMD driver download page and look through the release notes link, it has instructions on how to uninstall the old drivers and install the new ones.  I wound up deactivating the ubuntu-installed ATI drivers under SYSTEM, HARDWARE DRIVERS and running the general 11.6 install.  It wouldn't run aticonfig because I think the ubuntu install sets unusual file structures in place that the ATI  generic install doesn't undo, somehow.  Eventually, I went back to activating the ubuntu-installed ATI drivers and got my overclocks, so I was content.
I should have tried searching more.  Here's a wiki that details how to get 11.6 on 11.04, including a section on how to remove the ubuntu-installed driver config:
http://wiki.cchtml.com/index.php/Ubuntu_Natty_Installation_Guide