It still works with Aces High Version 2.20.3 as of today 17Aug2010. Here are some observations:
You need only download the .res file. No need to download any ".mis" file, as that one seems to be built automagically the first time you run the mission. You can get the required .mis file here:
http://techvideoreview.com/FlightSimMovies/AcesHigh/Ah2Missions/SolomonMelee/Ah2MissionSolomonMeleeFullPage.htmI just stored that "solomonmelee01a.res" file in my "missres" folder. At that point, there was NOTHING in my "misstemp" folder, but the mission showed up as one of my "offline missions" choices. I was able to fly the mission. After that, I saw that a file named "solomonmelee01a.mis" had been created in my "misstemp" folder.
Three more important items:
1: You will need the "solomonC" terrain, which you can obtain here:
http://techvideoreview.com/FlightSimMovies/AcesHigh/Ah2Terrains/Ah2SolomonIslandsTerrain.htm2: The computer-generated planes aren't very smart. They crash into the ground a lot. They were much, Much, MUCH better in Aces High 2 Version 2.13.1. That old version continues to be the best one for flying offline missions (and it properly supported warp segments too).
3: When you first start out in a P38, you'll be parked very close to a cluster of new trees that were never present in earlier AH versions. If you try to just taxi forward, you'll hit them, even if you try to turn away from them very hard. The only way I could turn hard enough to avoid a tree collision was to shut off one engine and goose the other, allowing my P38 to almost spin in place.