I downloaded a Revit 2012 file from a MEP engineer that won't load in Revit 2012 or 2013. I have used their Revit files before, but now it won't work. The error that occurs is "No element in a secondary option can be referenced by an element outside that option". This error can't be ignored and only cancel can be selected, which cancels loading the file. Any suggestions on how to fix this error? Here's a screenshot of the error.