Did you have an instance of MSDE installed before you installed backup exec? The default username and password is UN:admin and the password blank. I would try that as your log in account and see what happens.
How is your backup configured? In the general tab of your backup job properties do you have the tape drive set or a backup to folder set up? The configuration would be very helpful
I ran into the same issue, so I configured the Backup Exec account to notify me and send a backup log to my email account. It is sent in html format, and I can easily open it. This way I don't have to go through Backup Exec to open the log files