Could be a few things, certainly LB's suggestion is a quick fix if that's the case.
Otherwise it can be related to connectivity, such as using the Oracle ODBC instead of Crystal's native or ODBC connectivity.
A quick fix would be to use a SQL Expression or a Crystal formula to convert it and reference the formula, as in:
cdate({table.field})
or a SQL Expression might use a CAST or CONVERT statement, which would prove a bit faster as it's processed by the database.
-k