When you create a new object you can undo using CTRL+Z before you click in the layout to place the instance. This way C2 tries to add an instance of an object that doesn't exist and crashes.
Step by step:
1) Double click to add object
2) Before you place the object press CTRL+Z
3) Place the object
If it's a sprite, C2 crashes. If it's a text object or a text box, the object is placed, but there's no listing of it in the "Object types" list to the right.
I'm using Windows Vista x64 and Construct 2 r99.