If you are getting a Cannot make type. error when loading in type catalogs check to see if they contain fractions.
They switched to Visual Studio 2008 for Revit 2010 and are now using the decimal format, which requires all type catalogs to be in decimal format. The "Use decimal format" trigger that helped me figure this out is buried in the Families Guide for 2010.
Reveal Elements - Hidden Viewport
2 days ago