The provider name for SQL Native Client (SNAC) connections has changed in Katmai. Since this is the default provider for OLEDB connections, you'll probably be affected by this change if you're running SQL Server 2005 packages in Katmai.
When the full upgrade solution is in place, we'll prompt you on whether or not to upgrade your connections, but for this CTP, you have two options. You can install the SNAC9 redist that comes with SQL Server 2005 (it should work fine side by side with the Katmai SNAC10), or you'll need to manually edit your connection strings when opening Yukon packages in Katmai.
To edit the connections yourself:
You'll also encounter a similar issue for Analysis Services connections.
SNAC9 and SNAC10 should be fully backwards compatible, although there might be small changes in behavior due to bug fixes. For example, writing a DT_DBTIMESTAMP value (that contains datetime value with milliseconds) to a smalldatetime column using an OLE DB Destination used to work with SNAC9, but results in an error with SNAC10 ("The value could not be converted because of a potential loss of data"). These differences will be compiled into a KB article for the release.