As said in the dialog box, I opened mainScreen.xml saw that there were instances of "spike" there, but no object-type "spike" in the howdie2.0.capx.Get the fixed caproj file
Copy it at the root of the project folder (backup your existing file) and open it.
I created a "spike" object type with a sine behavior, no more no less.
Be sure to open your spike objects and maybe reset their origin/collision polygon.
I copied/paste elements from another object type, so the origin and polygon might be off. (I used the values of the "wall" object type).
If you can recall the steps that you followed before ending with this errorful caproj, I'm sure @Ashley would have a look at it to prevent it in future releases.Kyatric2012-02-05 11:38:31