I have downloaded AlliED and am getting to grips with it quite well, there are however a few things annoying me so any help would be extremely appreciated.
Firstly, all the missions i have downloaded of the net are played in order through the double doors on the cruiser screen but all the ones i create are only playable in the combat simulator. What am i doing wrong?
Secondly, does the briefing editor actually work? Whenever i try to make a briefing the game just crashes to windows instead of showing it.
I know these things don't really make any difference but i'm just a sad lonely Alliance addict.

The first problem sounds like you haven't given your missions a high enough number in your modified mission.lst file so XWA thinks you have already completed them, hence their being available in the Combat Simulator for "replay".
Either change their numbers to higher ones or create a new pilot (with no combat history) and it should work.

The second problem is a puzzle as the only cause I can think of would be having a misnamed mission file (missions with briefings need to follow a set format for their name, though missions without briefings don't need to), and AlliED's error checker automatically informs you of this.