Hi,
i've just notices that i'm getting "ERROR:nathelper:nh_timer: out of memory" each time it passes this section:
if (!allow_trusted() && client_nat_test("3")) { setflag(7); force_rport(); fix_nated_contact(); };
There are around 1.6GB of Memory free on this box, so i don't think it's a real OOM error ...