kdeartwork-3.3.0 looks for arts/k*.h some of which are not in /usr/kde/3.3/include after upgrading to kde-base/arts-1.3.0 i run an ~x86 setup, so this bug has likely not hit the general userbase yet. SUGGESTED FIX: kdeartwork needs to be patched, or told to look in /usr/kde/3.2/include
very similar to Bug #65352, marking it a depend.
emerge unmerge kdelibs emerge kdelibs emerge kdeartwork i don't know what caused this problem, but now it works for me.