You need to post a lot more information if you want help. There are no details...
Here is a guess at some of your issues though:
1) Corrupt data. Was this a mailbox backup by chance? If so, anti-virus which is running real time protection of email can cause this.
2) Directory is invalid. This can be caused by deleting a folder, or removing something from a database backup like an Exchange mailbox store, from an existing scheduled job. If the job cannot find something it was previously told to backup, it fails with invalid directory.
3) Authentication failed: Generally just a logon account rights issue. Make sure when you connect to resources, the default logon account you use in BE has full rights to the server, or provide a secondary account which does.
The above is just general issues to problems which may be the same as you are having. Post details and people here can narrow down your specific issue if the above info is not adequate.