I assume you are talking about the Mod's version of the Domestic Advisor. For now I would suggest turning off that option and use the native version. Also, could you cause the error and send copies of the 3 python log files(PythonDbg.log, PythonErr2.log, & PythonErr.log) from your My Games\Warlords\logs folder? (I think I remember you saying you had logging turned on.)
From the error message, I am thinking we have a problem with one of the translated strings not being handled properly. Any idea what you may have built, started building, discovered, etc. just before it stopped working? That may give us a clue as to which string.
You probably better go ahead and send the save file. I guess I can turn on german language to debug it. use the e-mail account in my signature.
I just send those files to you - note I am using the english language setting currently. I only noticed the error at some point during the game but now looked at the start save (I send you this one) and it is already there... so I don't think it is caused by any discovery... Also starting a new game with a different civ does not solve the problem

Edit: turning off the modified domestic advisor helps