recently I had a case when installer of SQL Server Management Studio got stuck on Loading Packages phase. And no move neither forward nor backward.
Luckily for me I found this suggestion in google:
running from an elevated cmd prompt:
reg DELETE “HKLM\SOFTWARE\WOW6432Node\Microsoft\Microsoft SQL Server Management Studio” /reg:32
As usually I'm reluctant with reg Delete commands, but here it seems I didn't have a choice. And that suggestion worked.