SQL & PL/SQL

Hey, I am trying to generate this oracle database report and getting this error message.
I am using SSRS 2008 to build this report and the query is not responding.

It give me: ORA-01858: a non-numeric character was found where a numeric was expected

When I run my Query in the builder, it returns perfect results, however if I try and run my Query through the report I made in SSRS2008, it gives me this error message. The Query is connecting to a PL/SQL database.

Here is my query.
Please I need help. Thanks in advance.

SELECT distinct

t.uniquenum,
t.doc_id,
t.doc_class,
t.BAIDS as Business_Account_ID,
t.doc_category,
t.doc_type,
t.trade_entity,
t.trade_id,
t.document_date,
t.trade_date,
t.inactive,
t.modified_by,
t.modified_date,
t.mime_type,
t.product_category,
t.term_matured_date,
t.doc_classification,
s.uniquenum

from fndept.sig_updated_docs_header t
join fndept.sig_updated_docs_detail s
on (t.uniquenum = s.uniquenum)


WHERE

(Trunc(modified_date) BETWEEN to_date(:BeginDate, 'mm/dd/yyyy') AND to_date(:EndDate, 'mm/dd/yyyy'))

ORDER BY t.DOC_CLASS, t.DOC_CATEGORY, t.DOC_TYPE, t.modified_date