You should check your modeler if you see an OSGi error/warning during startup (pretty sure it's a warning). Seems to be a problem with Calculated values converting from 4.x.x to 5.x.x
I have the same issue in a project that is created with Mendix 5.5.0.
One of the virtual attributes was easy to change into a stored attribute.
The other is not: it is intended to display a multilanguage attribute in the language of the user, like in this topic: Multi language design models. Results of a knowledge network day.
I had this error when calling a snippet of a generalized entity with a specialized entity.