help with pygresql and large objects

I'm new to postgresql and using PyGreSQL 2.4 I'm experiencing problems with
large objects. I can create them and destroy them, but can't open them to
read or write. Here is some sample code from the interactive prompt:

>>> import pg
>>> db=pg.connect(blah...)
>>> bigobj = db.locreate(pg.INV_READ|pg.INV_WRITE)
>>> bigobj.oid
18369
>>> bigobj.open(pg.INV_READ|pg.INV_WRITE)
Traceback (innermost last):
File "<stdin>", line 1, in ?
IOError: can't open large object.
>>> bigobj.error
'ERROR: lo_lseek: invalid large obj descriptor (0)\012'
>>>

I've tried single constants too, instead of OR'ing them, but nothing seems
to work. I always get the lo_lseek error. I'm probably just doing something
wrong, but I don't know what.

Any ideas?

Thanks,

Jason Jones
jonesj(at)awl(dot)com