Final error: 0xe000848c - Unable to attach to a resource.

Good Morning all , 

i have an sql server that i want to backup through another sever, when i am trying to backup files and folders from the SQL its OK, BUT when trying to backup the SQL databases it returns me this error message

Completed status: Faile

"Final error: 0xe000848c - Unable to attach to a resource. Make sure that all selected resources exist and are online, and then try again. If the server or resource no longer exists, remove it from the selection list. Edit the selection list properties, click the View Selection Details tab, and then remove the resource.

Final error category: Resource Errors 

"

i have add the credintials for the sql server to the BE 2010 Remote agent. and nothing new. 

is there any ideas about this issue. 

Mahmoud Azem