If you network card does not support ipv6 (which my via-rhine type motherboard net chip doesn't) then a line of output is put into your make.conf file which is later interpreted as an error. The fix is simple (Just put a # sign before this error message so that when it goes into the make.conf file as an output of the mirrorselect -a -s4 -0 >>/mnt/gentoo/etc/make.conf command it does not later get interpreted as an error.
This has nothing to do with the card and more to do with your network connection. It doesn't appear that mirrorselect is safe to use as described in the handbook from the LiveCD due to the presence of the ipv6 module. Is there a proper solution for this?
*** Bug 54379 has been marked as a duplicate of this bug. ***
Reassigning a stale bug to mirrorselect maintainer.
Mirrorselect versions greater than 1.0 should handle ipv6 propperly in all cases. please test and file a new bug if appropriate.