After fixing my previous error (setup/upgrade failed while performing action install) it looked like i was successfully upgrading my Exchange 2010 server to SP2, but unfortunaly i received the following error when updating the Mailbox Role.
This server role can’t be installed because the following roles aren’t current: AdminToolsRole
When i checked the registry i noticed a different ConfiguredVersion and UnpackVersion.
I changed the ConfiguredVersion to be the same as the UnpackedVersion 188.8.131.52
After that i checked the \MailboxRole\ registerkey and noticed that the Action key was back, so to be sure i also deleted that and rebooted my machine.
Thank you for your solutions! Your Blog was a great help!