FastPath call returned ERROR

Still trying to store and retrieve large objects, still having trouble.

Though I'd rather be able to set/get streams from the
PreparedStatment/ResultSet, I thought I'd try to use the postgres
extensions and see where I get with that.

Here is what I tried so far.

 LargeObjectManager loman =
((org.postgresql.Connection)con).getLargeObjectAPI();

int looid = loman.create();

LargeObject lo = loman.open(looid);

Everything seems to work as expected until I try to write a byte[] with

lo.write(b);  //b is some arbitrary byte array

The result is:

FastPath call returned ERROR:  lo_write: invalid large obj descriptor (0)

Any comments or ideas?

Andrew