While upgrading from one ITMS version to another via Symantec Installation Manager (SIM), one of the MSIs fails to install. Looking at the MSI log the following error was noticed:
Error 1606: Could Not Access Network Location
ITMS 7.x, 8.x
This issue may occur if there is an incorrect setting in one of the following registry subkeys:
In order to fix this issue, please refer to "Error 1606" error message when you try to install or remove a Microsoft program: http://support.microsoft.com/kb/886549
In this particular example, the issue was that the "Favorites" reference was missing. Under HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\User Shell Folders\, we had to add "%USERPROFILE%\Favorites" into the "Favorites" regkey.