SSIS Package Error when called from SQL Agent Job
I had similar problem earlier and what I found is because the creator of the Package and executor of Package were different user it was having some issues. 

To get around this issue, I had to protect the package with password and I used that password to access the package in my Job. 

You should give that a try, I hope it helps.

Also, is your package doing any distributed transactions? You may need to set authentication from Services for distributed transaction.