I recently updated 10.0.5484 to SP3 and then tried to install the DLO Agent by running "\\\dlo\setup.exe. All I got was brief flicker and then nothing. After perusing several similar threads, I found this...
Check the C:\WINDOWS\bkupinst.log file. Look for the last entry and see if you have a entry like
"01-19-2006,11:19:29 : ERROR: 2 - Failed to open MSI package \\\dlo\VERITAS Backup Exec For Windows Servers.msi"
Check your \\\dlo directory and see if the MSI file in it has the same name as the above log entry. If it does not, something got hosed in your last install or upgrade. For my SP3 update It looks like the installer made the necessary registry entry changes but failed to update the DLO directory files.
To fix, backup and then delete the files in the DLO directory. Then, either repair, reinstall, or update to the latest version of backup exec (10.1d?) The DLO files should get reinstalled.