http://imgur.com/F8xOX Basically it deletes/hides all windows once I click on them. For testing purposes, I removed all other parts which add custom windows (mechjeb, ISAmapsat etc.), however the bug also occurs on standard windows (pause menu asf.). I'm using v0.04. Here is what the output_log.txt says about the NullReferenceException: Clicked on the little "toggle calculation button". Keep working on it, it will be a great plugin and I shall gift you my firstborn, once you release a stable version.