A couple things here.
Why are you storing user stored procedures in a system database? You should never, ever be using a system database for user work or storage.
The service account that SSIS is using, does not have permission. Create a working database for all the cleansing tables and stored procedures that are needed to import the data.
I would also bet that you are not using any type of config file or config table. Create and use at least the config file so that you can modify things like directory paths, server names, etc... when moving the SSIS package from server to server.