The glib ebuild for glib-2.6.0 is broken because it looks in the v2.4 subdirectory for the glib tarball. There are two ways to fix it, manually change v2.4 to v2.6 or chop off the last version number. Included is a patch that does the latter [downside: gives QA warning]. The former will cause the same error when they release 2.8 or 3.0 unless manually fixed again..
Created attachment 46288 [details, diff] Diff to use automated sed script
*** Bug 74875 has been marked as a duplicate of this bug. ***
18 Dec 2004; Dylan Carlson <absinthe@gentoo.org> glib-2.6.0.ebuild: Fixed SRC_URI.