Why couldn't there be an easy solution -.-
Okay, I've thought about it, and it's getting interesting... I can't guarantee that I can find the correct answer, since I have to guess some stuff too, but I won't give up jet.
I've made the experience too tthat I had a problem here and nobody could help me, so I 'll try my best:
First i thought that there is somethign messed up in your Native-folder. For example, in strings.txt there are tons if informations for the sarranids
But you have the problem in muliple mods, and it's unlikely that the mods are broken too.
The I remembered that some texturefiles are "Common resources", that means they are used in every mod if you arn't replacing them with new one. So maybe there is a Commin resource for factions too. Yep, I 've searched through everything, but found only animations and textures.
Then, I saw that the sarranids are the "last" faction (in strings.txt, they are numbered from faction 1-6 plus some bandits etc.) means faction_6. But in the first mount and Blade there were only 5 factions, no sarranids. And when you said you installed mods I got an idea:
Maybe, you installed a mod for the old Mount and Blade, miraculously it's working in warband too (As far as I know they are using the same engine), but the faction_6 is missing.
So, maybe one of your mods installed someting from the old Mount and Blade?
Maybe there are files, wich shouldn't be there, in your General MountBlade Warband folder (with the CommonRes files etc.)
Or maybe you are using a savegame from the old mount and Blade?
I'm sorry that I can't be more precise, I don't know exactly how the only M&B is constructed, plus I can't see what your mods have done.
Before we tinker long, I think it's the best and fastest option if you reinstall M&B Warband.
Just save your "Modules" folder somewhere + your "Mount&Blade Warband" and "Mount&Blade Warband Savegames" folder.
It shouldn't take too long, (just 2-3 GB), your mods and savegames are saved and it should work again, if the mods havn't affected your native-module too.
regards:
a pretty brain****ed nightdragger