[dba-SQLServer] A puzzle re: differences between 2000 and 2005

I regularly use a dialog in my apps that contains a calendar and allows you
to set a date range, which values are then passed to a report using
InputParameters. The form works perfectly with a sql 2000 database but
apparently not with a sql 2005 database. Has something changed regarding
datetime fields in 2005? The forms and the InputParameters settings are
identical, but I get an error in the 2005 app. It's using Access 2000
format, and otherwise runs fine in Access 2000 and 2003. The form is slick
and I'd hate to stop using it. I cannot figure out what's wrong. If I have
to, I'll convert the database to SQL 2000 format just so I can continue
using this form, but that is less than ideal.

Anybody got a clue as to why this behaviour occurs? Or alternatively, a
popup calendar control known to work against a SQL 2005 database?

TIA,
Arthur