Could you please tell us how the system detected the tlp* interface this is
happening on? A few lines of dmesg output (or from /var/run/dmesg.boot)
before and after the tlp0: .... lines would do (and any following MII/phy
related lines).

What does "ifconfig -m tlp0" say?

Thanks

Martin
P.S.: http://www.netbsd.org/releng/releng-1.6.html will tell you that 1.6.1
is pretty close now.