The ebuild for dev-dotnet/xsp-0.14 doesn't move target files into the correct directories. It leaves them in /var/tmp/portage/... where they get deleted during postinstall process. Probably needs a minor fix, I just don't know enough about ebuilds to do it myself.
Created attachment 32735 [details, diff] xsp-0.14.ebuild.patch use einstall or emake DESTDIR=${D} emake DESTDIR=${D} works fine, so here's a patch
I actually just fixed this in CVS about 20 minutes ago. See bug #52969. Marking WONTFIX. Please search before posting bugs. Thanks for keeping us on our toes anyway. (: