When User Logon Reports is enabled, the Desktop Central agent in the client computers executes a VBScript during user logon and logoff to track these events. The VBS files should be associated with WScript.exe so that it gets executed when you try to open the file. When the user has associated the VBS files to be opened in an editor, for example, when the Desktop Central agent tries to execute this script, it does not execute as the default application has been changed. It just waits there till it gets timed out, causing delay in the logoff time. In such cases, the User Logon details cannot be tracked for that particular user. Restoring the file association will fix the issue.