This problem may occur due to insufficient access rights to the account, used for connecting to the target system .
This account should have administrative privileges. You may refer following steps for configuring backup of remote machines:
1) Create a new user on the remote machine. Make newly created user a member of local Administrator group only.
2) Start Backup Exec, create a Logon account with same username and password as that of newly created user. You may refer to following:
-Start Backup Exec
-Select Tools > Wizards > Logon account wizard
-Add new logon account, type in the credential for the new account.
-Make this account a common logon account.
-Complete the wizard.
3) Create new backup job by selecting remote machine and select this newly created account from window.
If while selecting the remote machine, it does not prompt for the credentials then after selecting the remote machine | select "resource credentials" | select existing logon account | click change and select the newly created logon account
You may refer to the following technote.
http://seer.support.veritas.com/docs/250649.htm
