One of the settings xml files has become corrupt and needs to be deleted, after which File Stream will start up properly again and the file will get re-created automatically.
Browse to the following Windows Folder location: C:\Users\User_Name\AppData\Local\FILEstream Ltd\FILEstream 4.x (User_Name is the user you are currently logged into Windows with. Also, AppData is normally a hidden folder)
This folder location contains, among other things, the xml files that store your File Stream panel, database and scan preferences. Keep in mind, recreating the xml file will restore those preferences to their default values. Pay attention to the error message you are getting as it should say which xml file is corrupt; eg: Settings.xml