ERROR: SET TRANSACTION ISOLATION LEVEL must be called before any query

I am getting this error reported back from JDBC.  I'm not sure if this is
from JDBC, or from the Postgresql 7.1.

Message:   ERROR:  SET TRANSACTION ISOLATION LEVEL must be called before any
query
SQLState:  null
ErrorCode: 0


It seems to occur if run two simultaneous "mass delete" operations.  It
appears as though the database connection goes away, since my code then
attempts to reconnect and I get repeated sql exceptions:

Message:   No results were returned by the query.
SQLState:  null
ErrorCode: 0

I have to restart the programs to get them oprational again.

Thanks,
David