I've had Legacy for a while. I played through the campaign four times now. But when I started a fifth round, (yeah, I like the story) the first mission won't start. I get that darn ACCESS VIOLATION crap. I tried other missions, and I discovered that some missions worked while others crashed before the loading finished! I only have the community mod version .002 installed. These are the ones that worked: The last three missions of Enterprise. The first mission of Kirk. The last mission of Picard.
A shocking number of mods cause problems with Legacy. For some reason Legacy seems very sensative to change, altering a pre-existing odf for example can cause the violation, but doesn't always.
The one that I have found to cause the most problems is the saving and loading mod. For whatever reason saving was not possible mid-game, and after using the addon that enabled it, many people got the Violation and never made the connection between the saving and loading and the error. Further more after removing the saving and loading addon some people found the Violation disappeared.
How do you fix it?
You must replace any "corrupt" files that exist within the game directory, so replace altered files with the originals, that is assuming you made backups. Failing that you will have to reinstall.
If it was something like a odf you added, the solution would be simple. Other than the essential items within the odf, whats in it that isn't in say the Intrepid odf.....so on so forth.
Additionally its worth mentioning that I have two copies of Legacy on my hard drive; one for other peoples mods and one for my own work. This way, it is much easier to find out if its my files that are the problem, or someone elses.