This error is usually related to Backup Exec Database access.
A) Logon to the Backup Exec server as the BESA Backup Exec Service account and open a command window. Start > Run > CMD), type the following and press Enter:
osql -E -S SERVER\BKUPEXEC
One of the following errors may be returned:
Login failed for users 'DOMAIN\'.
Cannot open user default database. Login failed.
[SQL Native Client]SQL Network Interfaces: Error Locating Server/Instance
Specified [xFFFFFFFF].
[SQL Native Client]Login timeout expired
[SQL Native Client]An error occurred while establishing a connection to
the server. When connecting to SQL Server 2005, this failure may be caused by
the fact that under the default settings SQL Server does not allow remote
connections.
The first error indicates there are authentication issues. It is necessary to ensure Backup Exec is correctly set up with an appropriately configured service account.
1. Log into Windows as the Backup Exec Service Account (BESA). This is usually the same account that is used to perform backups (re: the System Account under Backup Exec's Network > Logon Accounts Menu).
2. Make sure the Backup Exec Service Account and the Logon Account of the Backup Exec Services are using the same accounts. In the Network > Logon Accounts Screen, the Owner column of the System Account should be the BESA as well as the same account under the User name column; if changes need to be made to make these identical, perform the steps in the following article:
How to create a System Logon Account in Backup Exec for Windows Servers
SQL Server
The SQL instance hosting the Backup Exec database may have no default database associated with the Backup Exec Service Account. Open SQL Management Studio, then expand Security and select Logins; select the User account and right click and select Properties ...

In the Default database field, select BEDB as the Default database, then close out Enterprise Manager.
Return to Backup Exec and retry the report.