When noatun (kde 3.1 beta2) is started, it makes arts segmentation fault... I've tried to go back to arts 1.0.7 without success. xmms-arts works, so I think it is a noatun issue. See http://forums.gentoo.org/viewtopic.php?p=98703#98703 for details.
Solve it by changing flags to -march=pentium3 -O2 -pipe -fframe-omit-pointer and -O3 break things horribly (kdemultimedia and arts) Please change ebuilds to filter these optimization options.