This problem can happen in many areas of liveSite (installation form, login form, and etc.). The problem is caused by liveSite not being able to store session data for one of two reasons which are described below.
1) The web server might not be setup correctly to handle sessions in PHP. The administrator of the website should verify that the web server can write to the session.save_path, which is a setting in the php.ini file.
2) The user might have cookies disabled. The user should verify that cookies are enabled in his/her web browser settings.