Thanks.

I know there's a clue in the fact that with Gizmo I can't hear the call recipients (but they hear an echo of their own voice), and with Googletalk+gtalk2voip the recipients can't hear me (I hear an echo of my own voice), but be darned if I can figure it out yet. EIPI and I had similar issues going PC to PC; he heard me but I could not hear him. Odds are it is indeed my router. I am still experimenting with configurations-- searching on the subject has netted nothing useful.