For PostgreSQL v8 JDBC drivers the blob type maps to OID, not BYTEA:
from here: http://doc.postgresintl.com/jdbc/ch08.html
"....To use the Large Object functionality you can use either the LargeObject class provided by the PostgreSQL™ JDBC driver, or by using the getBLOB() and setBLOB() methods...."
When using PostgreSQL (v7 or v8) with the v7 JDBC drivers BYTEA works fine, but with the v8 drivers you get an error message:
ERROR: column "binvalue" is of type bytea but expression is of type oid