Ok, I knew it is probably just a checkbox to untick. But a digital immigrant I am I didn´t want to do something stupid. Fredericks suggestion led me to the idea to see if Microsoft Security Essentials might be the source for the wasted hours this evening. I deactivated it and surprise: the fuel planner starts again and is obviously working like it should. Thanks to everybody for the support helping me solve the problem. Thanks Aerosoft for a great product and all the best for