Windows 7 and later has a feature named FastUserSwitching. We all know about it, but ShoreTel do not understand it. The discussion about their setup bug goes back for more than one year now and they still do not listen after 4 case reopens. It is clear that ShoreTel development do not understand how thier own software and Windows works. So I decided to publish this information to help you running ShoreTel Communicator properly in your environment. This affect nearly every version for about 5 years or more, but has been fixed in Mitel MiVoice Connect R1803. If you may ask why FastUserSwitching need to be disabled - the answer is simple. ShoreTel Communicator's SoftPhone feature is not compatible with multiple users on the same computer. This VoIP EyeP driver under the hood does not allow more than one user on a computer.
FastUserSwitching is these neat featue you may like a lot at home. It allows users to login to a computer with several users at the same time without logging the other user out. A typical home users scenario.
Situation: