6.5 cvs ERROR: copyObject: don't know how to copy 604

Today, I tried cvs version of 6.5 and got following:

c_flats=> explain select station_id from metro_stations except select metro_id from work_flats;
ERROR:  copyObject: don't know how to copy 604
c_flats=> select station_id from metro_stations except select metro_id from work_flats;
station_id
----------       27       41       60       81       92      102      133      134      142      149      150
(11 rows)

Explain fails while select works (didn't check the result though)
Regards,
    Oleg

_____________________________________________________________
Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
Sternberg Astronomical Institute, Moscow University (Russia)
Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
phone: +007(095)939-16-83, +007(095)939-23-83