I get this error: /var/tmp/portage/kvirc-3.0.0/work/kvirc-3.0.0-xmas/src/kvirc/include/kvi_taskbar.h:191: friend declaration requires class-key, i.e. 'friend class KviTreeTaskBarItem'
I hit on the same thing and saw the bugreport and fix you (mkennedy) submitted on the kvirc.net bugtraq. I also got the same additional errors, starting with an internal compiler error. Will be glad to test any fix etc., right now I'm busy finishing setting up my gcc 3.1 system.
kvirc-3.0.0-beta1 was released a few days ago and it compiles perfectly with gcc3. Also, kde support is working again afaics (not sure why it was disabled in the xmas ebuild but there were some problems). I'm packaging the beta1, once that's done this can be closed.
beta1 committed (#4127).