Symantec Tape drive disappearing.

This is also other error message I'm receiving, the domain admin account has access to exchange database. The file server is Windows storage server 2008.....

Backup- \\Server\Microsoft Information Store\First Storage Group V-79-57344-33928 - Access is denied.
Access denied to database .
V-79-57344-33928 - Access is denied.
Access denied to database .
V-79-57344-33928 - Access is denied.
Access denied to database .
V-79-57344-33928 - Access is denied.
Access denied to database .
V-79-57344-33928 - Access is denied.
Access denied to database .
V-79-57344-33928 - Access is denied.
Access denied to database .
V-79-57344-33928 - Access is denied.
Access denied to database .
V-79-57344-33928 - Access is denied.
Access denied to database .
V-79-57344-33928 - Access is denied.
Access denied to database .
V-79-57344-33928 - Access is denied.
Access denied to database .
Backup- \\Server\D: DataMedia mount failed.
User canceled a Physical Volume Library operation.
V-79-57344-33861 - The media operation was terminated by the user.

In event viewer I am receiving a log also, this is the event info:

Source: Backup Exec
Event ID: 34113

Backup Exec Alert: Job failed
{Server:"Server name"}{Job: "Weekly Backup"}Weekly Backup -- The job failed with the following error: Access denied.

The Arcserve user needs to have access privileges to the disc being backed up - have you recently changed the Arcserve account settings, or the password?

I do not have an arcserve account anyware, its using the domain admin account.. I recently replaced the hardware for exchange, I migrated the everything over.. The additional windows storage server 2008 was added as well..

The external tape drive was bad, the internal fan is bad and damaged it.. So we are looking into alternative backup solution. Thank you for your help...