Oh just realized that you are trying for a new start rather than loading your game. What happened in 1141 that made you pick that date?
Anyway The problem is that SWMH primarily supports 1066 and maybe a few more years in and the 867 landmark. I remember a bug similar to that one long ago in another start date. Not sure on the specific cause.
I tried loading up the game as Poland and using "play 7903" (the id number of the emperor), which seemed to work fine. There may be other bugs further in, but that seems to work. Maybe an internal mechanic fixed the problem upon trying to load the game.
Edit: I think it may be caused by him owning the city holding in Vicenca (Basan), combined with an Agnatic Elective made the game think it was a Republic, yet not quite.