When using ASP.NET MVC 3 with a model that is nested, the missing single quote prevents the getModelPrefix value from properly validating.
This answer (http://stackoverflow.com/a/9523596/30505) on StackOverflow describes the problem. Ignore the part about remote validation.
As far as I can tell, that's not part of this plugin's codebase. I'm not maintaing that unobtrusive version.
Apologies - I'll try to follow up with the ASP.NET team as it shows up in ASP.NET MVC 3.