Had the same problem with a pcu50 panel (I assume that´s what you have got), don´t know why it began to popup the logon window. Found this on the Internet and followed:
Click Start Button (In service mode), Run and type CONTROL USERPASSWORDS2, and click Ok. Select the user account from the list (the account to which you want to automatically logon). Uncheck Users must enter a user name and password to use this computer option, and click Ok. Type the user account password and complete the process.
Hope this works for you to.