RELENG_7: /boot/loader command prompt mode broken?

[Eugene Grosbein]

Hi!

Today I've updated my 7.0-STABLE system using source upgrade path.
loader(8) boots it just fine but it's impossible to issue commands
using its command prompt mode (N.B.: beastie_disable="YES"
and autoboot_delay="2" are in my /boot/loader.conf).

At boot time, I hit "Space" button to reach its command prompt - that works.
While typing of a command, I observe one of bad things:

1) it just hangs solid (keyboard LEDs do not switch) after a couple
  of characters entered, or
2) system spontaneously reboots while typing, or
3) it shows endless flow of hex dump, presumably from BTX.

Most of time it hangs, a couple of times I've got reboot
and once there was hex dump. I use vidconsole with PS/2 keyboard.

Seldom I've allowed to type 'boot -s' and hit enter without a problem -
it boots system OK then. So, I assume there is a problem
with vidconsole input/output routines.

I've rebuilt /boot/loader using sources of 7.0-RELEASE and it works nice now.
My has Intel D975XBX motherboard, I use PS/2 keyboard.
What should I try to debug this?

Here is my /etc/src.conf:

WITHOUT_ATM=
WITHOUT_AUDIT=
WITHOUT_AUTHPF=
WITHOUT_ZFS=
WITHOUT_CDDL=
WITHOUT_FORTRAN=
WITHOUT_GCOV=
WITHOUT_HTML=
WITHOUT_I4B=
WITHOUT_INET6=
WITHOUT_IPFILTER=
WITHOUT_IPX=
WITHOUT_KERBEROS=
WITHOUT_PF=
WITHOUT_PROFILE=

And I have 'CPUTYPE?=pentium4' in /etc/make.conf

Eugene Grosbein