martti@netbsd.org <martti@netbsd.org> typed:
: I have a fresh installation of 1.5ZA (make release from last week)
: which I upgraded yesterday (build.sh, kernel, etcupdate, MAKEDEV).

Did etcupdate mean you updated /etc/ttys?  If you didn't, then any
ttys allocated which aren't listed in /etc/ttys will not have logins
entered into the utmp file since /etc/ttys defines the position of
entries within the utmp file.  If you want 600 ttys or whatever the
number is then you need those 600 tty lines in /etc/ttys.

Regards,
-- 
Geoff Wing : <gcw@pobox.com>
Rxvt Stuff : <gcw@rxvt.org>
Zsh Stuff  : <gcw@zsh.org>