Sql command not working with date time??

Question

I am using my own sql query to fetch data in the sql command.
Due to the problem I found - here is the basic example:
The sql is:
select to_number(to_date('10/11/2011 10:23:00','dd/mm/yyyy hh24:mi:ss') - to_date('10/11/2011 10:20:00','dd/mm/yyyy hh24:mi:ss'))  minu  from dual
But I am not getting anything in Crystal Report tool!!
In any sql tool I get results.
When I am not using time part (hh24:mi:ss) :
select to_number(to_date('10/11/2011','dd/mm/yyyy') - to_date('09/11/2011','dd/mm/yyyy'))  minu
from dual
I am getting data!!!!
What is the problem??
Initially I had it with parameters of type 'Date Time'
Please, any one knows what the problem is?

Answer 1

Hi,
Sorry for the delay and thanks for answering.
It was partial solution
Moving to oracle driver, not (OLE DB), this specific one worked fine:
select to_number(to_date('10/11/2011 10:23:00','dd/mm/yyyy hh24:mi:ss') - to_date('10/11/2011 10:20:00','dd/mm/yyyy hh24:mi:ss'))*100 minu from dual
BUT
When I tried to change one of the hardcoded values to be parameter of type 'Date Time' I couldn't pass the validation step - mostly the errors:
"ORA 00900 Invalid sql statment"   and
"ORA - 00907: Missing right parnthesis"
No matter which format I used.
Last version is:  
select to_date('{?tsStartReport}','yyyy-mm-dd hh24:mi:ss') from dual
Any idea why 'Date Time; is so problematic? How can I workaround it?