Don’t hide or disable menu items…

Firefox 'dialog' The suggestion by Joel to not hide or disable menu items is a good one. There’s only one issue. With the way it’s worded you could end up with a swarm of dialogs. I would suggest some form of stackable notification item. The status bar isn’t really suitable for this as there’s no way to get stuff back from it historically.
The ‘in frame‘ dialog that’s becoming popular these days in such browsers as Firefox. This is a reasonable ‘dialog’, and you could remove them automatically after a period of time (say 30 seconds). as long as they are differentiated from the other items on the screen it would be reasonable.