The hostap driver included in linux-2.6.16 has a bug with EAPOL frame encryption causing disassociation of all STAs when the hostap driver in Master mode rekeys the GTK. Please include the the "Fix EAPOL frame encryption" patch from the upstream bug report in genpatches-2.6.16-x.
fixed in gentoo-sources-2.6.16-r1 (genpatches-2.6.16-2)