The ftp site for the patch for the version of sash in the portage tree no longer exists. I believe that is because the revision has rolled forward to 3.6 (if memory serves) That ebuild does exist, however, I don't know how to make "emerge -u system" use that one instead of the broken one.
I just managed to fetch it from both Gentoo mirrors and its upstream site. Can you show a paste of the fetch error?
Yeah. Looks like the site went down. Fixed in CVS.