Loads of reports using SQL server 2008R2 won't work in Server 2012 - get database logon failed

Hi

We have generated loads of Crystal reports for our .Net Framework 4. ASP.Net application using SQL server 2008R2, we are now migrating to SQL server 2012. Our reports will not run in the new version unless we load the Sql client for SQL Server 2008.

We take our connection string from the web.config using System.data.sqlClient and rewrite the string via c# in a ASPX page.

We were using 13.0.3 and have migrated to 13.0.15

How do we migrate all our reports so that they use the SQL server 2012 driver?