Nut upsuser - May 2013 - My nut-snmp has forgotten how to speak IETF RFC1628!

[I had a look through the mail archives before sending this, but I
didn't find anyone else having this issue.]

Has anyone seen this before?  I'm almost 100% certain I tested this
nut correctly detected OB LB in the past, but when I happened to look
at it today, I see it refusing to work -- apparently because the NUT
client knows how to ask for RFC1628 OIDs, but not what to do with the
responses.  WTF!

    # /lib/nut/snmp-ups -a GE-EP3000 -DDDDDDDDD
    Network UPS Tools - Generic SNMP UPS driver 0.47 (2.4.3)
       0.000000     debug level is '9'
       0.001846     SNMP UPS driver : entering upsdrv_initups()
       0.001860     SNMP UPS driver : entering nut_snmp_init(snmp-ups, ups, v1,
public)
       0.030096     SNMP UPS driver : entering load_mib2nut(ietf)
       0.030123     load_mib2nut: trying ietf mib
       0.030132     nut_snmp_get(1.3.6.1.2.1.33.1.1.1.0)
       0.032006     [GE-EP3000] unhandled ASN 0x5 recieved from
1.3.6.1.2.1.33.1.1.1.0
       0.032019     Unknown mibs value: ietf

If I leave out mibs=ietf, I get the same, only it tries other MIBs
first, and the last line changes to

       0.051158     No supported device detected

Here's my config, which I'm almost certain worked before.
AFAIK nobody has fiddled with the UPS settings, either.
Is the problem in nut or in the UPS?  (Looks like nut to me.)
Has anybody seen this before?
A na?ve "apt-get --reinstall install nut nut-snmp" didn't help.
I'm using version 2.4.3-1ubuntu3.2 on Ubuntu 10.04.

    /etc/nut# grep ^ *
    nut.conf:MODE=standalone
    ups.conf:[GE-EP3000]
    ups.conf:driver = snmp-ups
    ups.conf:port = ups
    ups.conf:mibs = ietf
    upsd.conf:LISTEN 127.0.0.1 3493
    upsd.users:[local_mon]
    upsd.users:    password = UNPRINTABLE
    upsd.users:    upsmon master
    upsd.users:
    upsmon.conf:MONITOR GE-EP3000 at localhost 1 local_mon UNPRINTABLE master
    upsmon.conf:POWERDOWNFLAG /etc/killpower
    upsmon.conf:SHUTDOWNCMD "/sbin/shutdown -h now"
    upssched.conf:CMDSCRIPT /upssched-cmd

There's definitely something listening on the other end, because when I
go into the UPS's web interface and change the SNMP community from
"public" to "*", I get different output.