exchange backup jobs failing on western digital nas storage

i have exchange database wich is about 64 g.
when i want to backup it`s database on the WD NAS storage it start and backup the 99% of database but when its want to finish it give me an error that says access denid
i also backup sql database which is about 1 g on WD NAS storage but it complete successfully
i can successfully backup exchange database on its local backup server
i backup with symantec backup exec 12.5

so please help me

[quote]i have exchange database wich is about 64 g.
when i want to backup it`s database on the WD NAS storage it start and backup the 99% of database but when its want to finish it give me an error that says access denid
i also backup sql database which is about 1 g on WD NAS storage but it complete successfully
i can successfully backup exchange database on its local backup server
i backup with symantec backup exec 12.5

so please help me[/quote]

You might want to start of with the list of agents? How you backup to the NAS Storage, via file dump? :)