The Simulator for Arduino is designed to be as easy to use as possible and bug-free. However, this depends on the level of complexity of the Arduino sketch being simulated and from time to time, the Simulator may not work as expected. In these rare and very infrequenct cases, please email support@virtronics.com.au or else post on the forum at forum.virtronics.com.au and someone at Virtronics will try to reply as soon as possible - usually withni a few days.