All I was attempting to do was add another high-level planet to my initial solar system.   My custom faction (defined in-game, not through the mod) uses Sol as it's home star so I modified StarSystemsDef.xml and changed the definition of SolSystem - putting all the planets into the HabitableZone OrbitLane.   Then I modified PlanetDefs.xml to change PlanetClass and set PlanetType to Habitable.   I also have the PlanetTraitDefs.xml file in the same folder, but I don't think I've made any changes to it.    It was just still hanging around from when I was originally tinkering with the mod.

The weird thing is, this WORKED before.   I still have my save game from August where I clearly started a game and my home system has the planets in it that I defined in the mod.   And when I tried to start a game yesterday it wasn't working.   I assumed that it stopped working because Steam installed updates to the game, but nothing I've been able to do seems to be able to get it to work again.

Also - I verified that all of the files I modified do not seem to have been changed since the last time the mod worked.   I thought maybe if there was a newer version of any of these three files it might require me to re-modify the new versions.   But that wouldn't seem to be necessary.   And besides, I would expect to get some kind of error message if that were the case.

In fact, I even got so exasperated that I put the modified files in the 'source' directory under /games/Steam/.... and it still didn't seem to have any effect.   That's what makes me think I'm missing something fundamental here.   I'd buy that I did something wrong with the mod except for the fact that it worked just a few months ago.

OK, situation resolved - sort of.    It appears I was running version 1.90, which is the beta version of the new release.   I'm not sure, but I think it is safe to assume that mods were 'turned off' for the beta.   I went into steam and opted out of the beta and that re-installed the 1.8 version of the game, and my mod immediately started working again.

It doesn't explain how the game was working when I deleted the two xml files from the Steam folders.   Maybe the beta pulls these files from somewhere else or something, or has the same xml code elsewhere.   I have no idea on that, but I suppose it doesn't especially matter.

I'm constantly experiencing issues with modding.  The 1st attempt will show up (if it works properly); but any changes after that seem to be moot.

So, it seems I have to do 2 things: 1 is disable my virus protection (as it doesn't like things being changed: created is fine; but not changed); and 2nd, I have to (re)verify the local files (via Steam; especially if I'm "on-line" at the time).

Hope that helps.

SK

I tried tinkering around with the files in the steam directory at one point, but that was only to see if I could 'force' it to use my mod.    That didn't work.

Now I am running into the same thing.    After I downloaded Crusade, I tried to re-install my mod by changing the new versions of the xml files.    I had a few missteps where the XML was bad and I was prompted with the errors.    I eventually got past that, but apparently whatever I had at that point would cause the game to crash when it was in the 'galaxy creation' steps. 

And I'm back to the same place I was before.    Right now, ANYTHING I do to my mod files doesn't seem to make a difference.    I understand that there could be something fundamentally wrong with my xml files, but even so, if I go out and change all three xml files' extensions from '.xml' to '.xmlsave', that should basically disable my mod, right?    There aren't any '.xml' files in the /mods subdirectory.    But it still crashes.

It is as though the first 'working' version of the mod that got past the syntax checking is somehow locked into place and no matter what I do, it will not refresh.

I am trying the 'verify files' option in steam.    The first try it told me there were 22 files that needed to be re-acquired.   The second attempt it said that all the files verified successfully.   Renamed all the '.xmlsave' files back to '.xml', restarted the game, and it crashed again.   

The only way i can get a game to start is if I go into the options and turn off all mods.    

Next I tried moving all three mod files out of the c:\users\.....\game directory into c:\temp.     When I do that, the game will start.   That is with all of the \Mods folders completely empty.

Then I tried copying the xml files from \temp back into the \Mods\MyMod\Game folder one at a time.    It seems like the game still crashes if any of them are there.

As a last resort, I kept just two of the xml files in the \Mods\MyMod\Game folder and copied the 'distribution' copy of the files out of the steam directories where the game is installed into the \Users\....\Mods\MyMods\Game folder.    So what is actually in the \Mods folder should be unchanged.    It still crashes.   As a last resort I tried turning off my anti-virus program, and that didn't make any difference either.

Once you create a mod or make a change to an existing mod, is there something else you need to do - some other program you have to run - to enable it, or verify it or something?

Yes, I am putting my mod in c:\Users\MyName\Documents\My Games\GC3Crusade\Mods\MyMod\Game.

I noticed that I still had an old version of the mod, along with a mod I downloaded in c:\Users\MyName\Documents\My Games\GalCiv3\Mods.    I deleted all of them, but it still didn't make a difference.

I'd be glad to do so, but I'm not sure it's really necessary.    Here's what I have right now.    Three files I copied from E:/Games/Steam/SteamApps/common/Galactic Civilizations III/data/Game into C:/Users/MyName/Documents/My Games/GC3Crusade/Mods/MyMod.    The three files have not been changed from their original state.   So as I understand it, I basically have a mod in place that contains three xml files with no changes.    Basically, a mod that does nothing.    And it still causes the game to crash.

However, I just looked a little closer into the Steam directories.    There appears to be a E:\Games\Steam\SteamApps\common\Galactic Civilizations III\DLC\EXP2_Crusade\Game subdirectory that contains some familiar-looking XML files.    Let me try copying those versions of the XML files into my mod directory and see what happens....

And, it works.   Or at least, the game starts in an un-modded state.    So I guess all this time I was modifying the wrong xml files.   I guess we can chalk this up as an ID-10-T error.

Thanks for your help everyone!