Hmmm, it's a familiar problem, but I can't quite recall the quick easy answer... so you will need to check the following:

* campmap/names/heroes.txt - have you set up "famous kings" and a name list for your new faction? Especially check if you DO have a famous kings list, that you have the right number entered in the first row - the most common error.
* startpos/ ...txt - have you declared faction, declared it as FN_MAJOR, set start king, placed him, selected his number correctly (sounds like you have though)
* loc/(ENG)/names.txt - do you have translations for all your names? If not you will get a translation error message rather than a blank name, though... have you missed a " [ ] { or } anywhere in this file?
* loc/(ENG)/faction_specific - do you have all the entries for your new faction?
* what in-game name did you use to declare the faction in your startpos? Not sure how NTW does it - FN_Name or FN_Number? If you use FN_Number then you must declare all numbers consecutively (ie if you have an FN_20, you must also have FN_00 to FN_19)

That should be enough to look at for now My money is on the first one though