I was looking why Opera no longer will play YouTube clips, and searched forum and came across this thread. the last bit about the .macromedia.sav
suddenly showing up. I am wondering if this is one of those, 'safety' measures when you upgrade an application that the existing settings get saved for you to recover easily your custom settings.
As an example one could early loose kde4
settings when updating (and sort of without thinking about this until the damage was done)
Because of the .old can be used by others I have taken to add .my-initials
(slight gnome problem here), or .my-frist-name
those two is unlikely to be used by any upgrade program.