tgname munged

Can anyone explain why the following query (used by AQT to display its tree):

SELECT trig.tgname,
tab.relname,
case trig.tgenabled
when '1' then 'yes'
else 'no'
end,
trig.oid
FROM pg_catalog.pg_trigger trig,
pg_catalog.pg_class tab,
pg_catalog.pg_namespace nam
WHERE trig.tgrelid=tab.oid
AND tab.relnamespace=nam.oid
AND nam.nspname ='public' -- ?
ORDER BY 1

produces tgname like (from memory) RIFKConstraint...<number>
while without the ORDER BY (and it doesn't matter how you identify the column) tgname displays correctly (well, the same as what you see if you SELECT * FROM pg_trigger).

thanks,
Robert