It fixed itself! I had BoolProp on. Maybe that's why. I don't have OFB and it works for me. The only problem now is that in the relationship it doesn't show married. Only to the last sim I married them too. But they have the memories. That's good. I think Inge said something about that. I thought they fixed it though.

Hey people! I'm having some problems, so I'm going to ask if I'm doing something wrong, or if my computer is. Here goes: It works! Not.  I can go through the whole thing, but right after the wedding (female to male, adult to adult) the 'error!' message shows up! I have tried re-installing in case I missed something. I only have nightlife, so maybe it requires another EP. But the thing is, it works almost perfectly, I have no trouble placing it on the lot, and no trouble with the option to marry several people, but RIGHT AFTER the ceremony the error thing pops up! I know not to press delete, so I have been pressing reset, but that resets to before the wedding occured! Can someone tell me whats wrong?!! 
This is a GREAT idea, by the way. Now I can make a Big Love family for myself!