Whats in a name? Well quite a lot when it comes to loading data into Oracle using SSIS. The details are described here but it boils down to using "Oracle Provider for OLE DB" rather than "Microsoft OLE DB Provider for Oracle".
The difference? Well as the article states:
[Microsoft OLE DB Provider for Oracle] has not been enhanced since Oracle 8Therefore it doesn't support certain data types and 64-bit for starters.
Bear in mind however you need to install the Oracle client to get the Oracle Provider for OLE DB which is here.