http://www.symantec.com/connect/forums/job-logs-dont-work-firefox

The above suggests turning off javascript in Firefox which will then display the Backup Exec Html log file fully expanded.

On my Chromebook Developer Mode running Ubuntu 13.04 GNU/Linux inside a crouton change root system the menu option to disable Firefox's javascript has moved from what is described above it is:

Edit ==> Preferences ==> Content ==> uncheck the "Disable Javascript" option and then load the Backup exec file from disk.

(My version of Firefox is 22.0)