Hi rrdad,
Thank you for using Microsoft Windows Vista Forums.
It happens if there is a registry change in the Userinit value.
Follow the instructions below which will help you in resolving the issue.
1. Start > Run > Regedit > Ok.
2. Now navigate to the following key:-
HKEY_ LOCAL_ MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
3. Look down the list in the Right Hand pane, scroll down to the value Userinit This value should read: C:\WINDOWS\system32\userinit.exe, (The comma at the end must also be there)
4. If the value is different from that mentioned above then Right Click on the Userinit value and, from the drop down menu, select Modify. Type in the value **C:\WINDOWS\system32\userinit.exe,**in the Modify dialogue box click OK.
5. Exit the Registry.
6. Restart your computer.
Click on the links below for more information.
http://support.microsoft.com/kb/899865
http://support.microsoft.com/kb/555294
Please post back and let us know if this has helped to resolve your issue.
Regards,
KarthiK TP