According to what I've found on Google, your error is a privs problem for a non-SA account. If it's been running fine for years and suddenly quit like you say, then there's a very high probability that, somewhere and somehow, someone changed the privs for the related account or for the SQL Agent account.

Sorry I can't offer much more than that. You may have to more closely isolate where the problem is happening and simply deduce where the privs changes occured (for whatever reason) from what occurs in the code or the SSIS package nodes.