Unfortunately there was a bug (logged as 49206) in handling types exposed via ‘ExposeType’ method.
This bug was fixed and new Script for .NET sources are available at
To expose some CLR type you need to call ExposeType with 2 parameters - type itself and name that will be used in the Script to call this type (by default type name is used). After this this type can be instantiated and accessed via code like (assuming that JSType is a name (or alias) of exposed CLR type)
var t = new JSType();
t.SomeMethod(); // Accessing instance method
JSType.SomeStaticMethod(); // Accessing static method
Hope this helps