What has been changed recently?
Someone has made a change to the Server set up and saved those changes using the Enterprise Management server. This in turn has changed your config.xml file under c:\programdata\Qlikview and entered your username and password into the file. Open the XML file in an editor and search for "user" You will find two lines , one with user one with pwd and they will have values associated with them. Delete the user and password values and save the config file. Save the config file. You might want to back up your original file too. You should be able to find the original answer to this error on the community.