Final error: 0xe00084f4 - An unknown error has occurred.

Hi there.

I'm still having a nightmare with backup exec at one of our customers sites. i've just upgraded it to 2010 r3 but it hasn't made a difference.

I've tried a different NAS and also tried backing up to another server, really running out of ideas now. Below is the most common error log...

Any help would be greatly appreciated! 

Job ended: 16 May 2013 at 16:43:36
Completed status: Failed
Final error: 0xe00084f4 - An unknown error has occurred.
Final error category: System Errors

Backup- E:Storage device "Server02 B2D" reported an error on a request to write data to media. Error reported: The specified network name is no longer available. V-79-57344-34036 - An unknown error has occurred.