The screen sharing feature of GoToMeeting was never designed to be used as a troubleshooting or support tool. While the keyboard/mouse control it is great for collaborating on business documents, it frequently becomes unresponsive when you encounter anything that requires elevated permissions. Usually this is in the form of a Windows User Access Control prompt or Mac security dialogue. There is absolutely no way to proceed unless the local user at that computer bypasses the prompts or moves the mouse away from the program that requires administrative control.
If you are attempting to use GoToMeeting for technical support, we recommend you switch to our GoToAssist product, which is designed to run at an administrative level. This will allow you to interact with permissions dialogue without having to have someone physically present at the computer you are connected to.