I've now finished mission 4 (IMPORTant Business) two times. The first time I completed the next two missions as well. This time I quite just after starting the next mission.

When I go back into the game the Continue option from the main menu is unselectable. In addition I have no option to start from any mission after Mission 4. I can load my save game from inside Mission 5, so its not a big deal, but I'd like to know if I wanted to go back and try a previous mission later I could do that without working my way all the way from Mission 4 each time.

Any ideas?

That Continue option is a little strange, I think it's supposed to load your last saved game but if you quit out of a game or end unexpectedly it doesn't work. If you're mid-game, you're better off just saving when you quit, then using the Load option to continue your scenario. I only use Continue when I completed a scenario the last time I played.

On the opening scenario screen, you should be able to flip back and forth to replay any of the scenarions you've already completed.

It still wasn't working, but I found a cheat via google that unlocks all missions. When I did that and could cycle through all missions I discovered that mission 4 was not marked as complete but mission 5 was. It must be some way I'm beating that mission that causes it to not complete right. Oh well...thanks for the advice...I'm not using Continue again just in case thats what messed me up to begin with. :-P