driver fails to handle strings in query statements properly

I am using jdbc7.0-1.2.jar. I am getting a "No class found for
unkown" when I use strings in my query statements such as 'Container'
seen in the query below. These queries work fine when I use Oracle or
MySQL. This looks like a bug to me. I can work around this by
explicitly casting the string in the query statement like:
'Container'::varchar.

*****************Inside LDMSQLPLUGIN About to query db ----> select
container_20_ft_qty AS QTY_OH, 'Container' AS NOMENCLATURE from
ue_summary_mtmc
where uic = 'WAQJAA'
EEEEEEEEEEEEEEE I caught an exception on resultSet.getObject(i + 1) -->
Container
No class found for unknown.
at org.postgresql.Connection.getObject(Connection.java:621)
at org.postgresql.jdbc2.ResultSet.getObject(ResultSet.java:741)
at
org.cougaar.domain.mlm.plugin.ldm.LDMSQLPlugIn.executeSQL(LDMSQLPlugIn.java:432
)

Is there a fix for this?

Thanks in advance,

Lora Goldston