parser: parse error at or near "-"

hi,

I am developing an accounting application using postgresql 7.2.2 and pg72jdbc2.jar. I met following exception when execute a query:

java.sql.SQLException: ????: parser: parse error at or near "-"

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)
at org.apache.commons.dbcp.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:179)
at db.TeleRateTable.selectAll(TeleRateTable.java:36)
at org.apache.jsp.admin_jsp._jspService(admin_jsp.java:737)
......

the sql string is:
select * from teleRateTable ORDER BY char_length(prefix), prefix LIMIT ? OFFSET ?

Any hint on solving this problem is appreciated.

regards
zhanyi