Enabling UAC causes Blank Screen on Logon

Thank you for your guidance.

I followed your instructions for both the Method 1 Clean Boot and the Method 2 System File Checker.

Method 1 Clean Boot ... I enabled the Clean Boot in Safe Mode and then rebooted normally.  With UAC enabled, after I logon, the screen went blank after 30-60 seconds with just the mouse arrow cursor shown (moving mouse moves arrow).  I waited 5 minutes and the blank screen never changed.  My keyboard is active so I hit Ctrl-Alt-Del and either log off or restart from the ctrl-alt-del screen which shows up normally.  By the way, if I reboot into safe mode I can logon normally.  I did that and disabled UAC and then rebooted to run normally.  With UAC disabled, the logon executed normally.  Unfortunately, it appears that the Clean Boot did not change the logon experience.

Method 2 System File Checker ... I ran cmd.exe as administrator and performed "sfc /scannow".  SFC ran completely and posted  this message "Windows Resource Protection did not find any integrity violations".  It is my understanding that this means I have no missing or corrupted files.

If you need more info, feel free to ask.

I should mention that my UAC issues started when I tried to enable it and it gave me "The User Profile Services service failed the logon. User profile cannot be loaded." when I tried to logon to my normal admin account that I have always run in.  I was adviced to try replacing my User>Default Directory with contents from a another computer that is running fine with UAC.  I have a laptop running Windows 7 Pro versus Windows 7 Home Premium in the computer with the UAC problem.  I renamed my original User>Default folder and copied in the folder from my laptop.  The accounts I am trying to diagnose with you were created from the copied Default.  Before ... Any new account I created with my original Default Folder would give the User Profile Service error mentioned above.  After creating user accounts with the copied Default I got the Blank Screen behavior.

I hope I haven't confused matters ... If I have, I apologize and will answer any questions to clear things up.

In all cases, my system runs fine with UAC disabled and "not fine" with it enabled.

Thank you for the follow up.

I am in a home WORKGROUP I set up, but I am not in a DOMAIN.  I checked this via COMPUTER>PROPERTIES>ADVANCED SYSTEM SETTINGS> COMPUTER NAME tab which showed my home WORKGROUP and no DOMAIN (Network ID is greyed out).

If more info is required, feel free to ask.

Thank you for the suggestion ...

I did the following (Note that I have my normal admin acct and no other as a baseline and everything works fine unless I enable UAC then I get login fail with my admin acct.  Everything works in Safe Mode).

0 - Initially UAC is disabled and I only have one account (Admin with Password) ...

1) I created two new admin accounts (one with password and one with no password).

2) I restarted and logged into the two new accounts and my original admin account with no problems (UAC disabled).

3) While in my original admin account, I enabled UAC with "do not dim" as you suggested.  I rebooted.

4) When I try to login to the two new admin accounts both behave the same ... After 30+ seconds the screen goes blank and the cursor arrow is shown (can move around).  The keyboard is active because I can do CTRL-ALT_DEL and get its Windows Menu.  From there I can logoff and get back to the screen showing all users so that I may select and logon.

5) Note that if I try to login to my original Admin account, I get a logon failure (unable to load).

6)  I then reboot and get into SAFE MODE where I can logon to all accounts OK  with UAC enabled.  There I go in and turn off UAC and reboot normally.  With the UAC disabled, I can logon to all accounts (two new admins and my original admin account.

As an aside, I tried creating a standard user account and with UAC off, I got a logon failure (unable to load settings).  Initially I created it with no password.  I then gavve the standard account a password and it started to load, but then I saw a logging off screen and it went back to the screen showing all user accounts available for logon.

In any case, thanks again for your suggestion, but the results were the same as before ... With UAC enabled (even at the do not dim level), logging on does not work properly.

This is an update ... I decided to try a "non-destructive" install of my Windows 7 Home Premium to see if it would clean things up.  I won't go into the details of how I did it, but the result of this non-destructive process is that my Windows is reinstalled back to the beginning state and all my programs and files are preserved (had some issues that I needed to clean up, but all in all okay).

After the reinstall, my blank screen with cursor arrow problem on logon was gone.  I could logon and Windows would come up normally with UAC enabled.  I am discovering some quirks of running with UAC enabled, but that is not specific to this discussion.

I do not know specifically what was the root cause of the problem discussed here, but I do know that the reinstall got me back to expected performance.

Thanks to all for your time and consideration.