As per summary, please test and mark stable.
It appears that the requested version -6.3 has been dropped from portage! archtester xen-tools # eix squidclamav * net-proxy/squidclamav Available versions: 6.1 ~6.4 Homepage: http://squidclamav.darold.net/ Description: HTTP Antivirus for Squid based on ClamAv and ICAP
Since 6.3 is dropped by Diego, I guess him meant 6.4. There is no open bugs and is in tree since 2 months.
On the likely chance of it being the correct target, amd64 all ok
x86 stable
+ 26 Oct 2011; Tony Vroon <chainsaw@gentoo.org> squidclamav-6.4.ebuild: + Marked stable on AMD64 based on arch testing by Agostino "ago" Sarubbo & Ian + "idella4" Delaney in bug #388063.