Using a preparedStatement containing Oracle's to_date

Hi, I'm relatively new at programming w/ JDBC, so any help would be appreciated.

I am attempting to set a java preparedStatment parameter within Oracle's
to_date function.  However, if I do so, a blank query is always
returned (no exception is thrown).

The prepared statment contains something like this

...
where x.mydate = to_date(?, 'DD-MON-YYYY')
...

later on, I use setObject to set the parameter's value:
prepStmt.setObject(paramNumber, someString)

someString always contains a date format that is readily converted
using to_date within SQL Plus.  I have tried running the same query
within Oracle's SQLPlus, and have not had a problem.  I have also tried using
prepStmt.setString()(although this is not general enough for my code)
and a blank query is still returned.

Thanks in advance to anyone who responds.

-Jeremy