The new way of transparent proxy in squid 2.6.1 is quite buggy in this version. Please take a look at this bug : http://www.squid-cache.org/bugs/show_bug.cgi?id=1650 I have the same problem with the current 2.6.1 ebuild. Applying the proposed patch solves the problem for me (this patch seem not to be present in the 20060710 patchset bundle) Please, apply this patch !
The patch tarball was made to deal with constant flux of patches published at http://www.squid-cache.org/Versions/v2/2.5/bugs/. The new version do not have such page (yet).
Fixed in 2.6.1-r1. The new revision is based on squid-2.6.STABLE1-20060711.