Exchange 2010: Cannot log on to MAPI with the specified credentials. Review the resource credentials for the job, and then run the job again.

I'm using exchange 2010 on an sbs 2011 standard box. I've been getting frequent back up failures with an error message of "Cannot log on to MAPI with specified credentials ..." I've seen articles regarding this for users who are running exchange 2003 and 2007 but no exchange 2010. What is meant by resource credentials, and how do I check them?

Thanks in advance.