unterminated quoted string

Having the code

String SQL = "SELECT COUNT(*) FROM Destination WHERE address=?";
st = conn.prepareStatement(SQL);
st.setString(1, address);
rs = st.executeQuery();

and if address is an empty string, sometimes (very rarely) i get

java.sql.SQLException: ERROR: Unterminated quoted string

at org.postgresql.core.QueryExecutor.execute(QueryExecutor.java:94)
at org.postgresql.Connection.ExecSQL(Connection.java:398)
at org.postgresql.jdbc2.Statement.execute(Statement.java:130)
at org.postgresql.jdbc2.Statement.executeQuery(Statement.java:54)
at org.postgresql.jdbc2.PreparedStatement.executeQuery(PreparedStatement.java:99)

I use PostgreSQL 7.1 and PostgreSQL 7.2 driver with "compatible=7.1" option.