Actually the Native 10 driver is shipped with SQL 2008.
It can be a problem depending on which driver you used in CR, ODBC or OLE DB.
If ODBC then just update your DSN to use the Native 10 client dll, if OLE DB then nothing needs to be updated but I would recommend Verifying each report after manually updating the connection info. It's only 50 reports so should be quick.
What this will do is verify the user has access to the tables, lot's of security changes in 2008, and the DB driver may have been updated as well. MDAC drivers are not 100% supported with newer DB Servers according to MS.
Don