"could not open relation..."

I saw this in the postgres log. Anyone know what would cause this?
Thanks, Brian

postgres 8.3.5 on RHEL4 update 6

[3358-cemdb-admin-2010-04-09 04:00:19.029 PDT]ERROR:  could not open
relation with OID 170592
[3358-cemdb-admin-2010-04-09 04:00:19.029 PDT]STATEMENT:  select
lm.ts_login_name,sm.ts_session_id from ts_user_logins_map lm join
ts_user_sessions_map sm on sm.ts_user_id=lm.ts_user_id where not
sm.ts_soft_delete and not lm.ts_soft_delete and lm.ts_user_id != 1 and
lm.ts_app_id in (600000000000000001) order by sm.ts_creation_time