blank screen after logon

Have you tried startup repair after blank screen

Have you tried SFC \scannow

TC,
Fluff out your System Specs for us please.

Update your SevenForums System Specs
User CP (located on the top menu bar) |
Your Profile | Edit System Spec (left-hand column)

To gather info, use Speccy (my favorite) or SIW or System Info

ADD the word laptop or desktop or netbook to the
“system manufacturer” block, for example,
Toshiba Satellite L305D notebook.

Provide full windows version info, for example:
MS Windows 7 Ultimate SP1 64-bit

Use the “Other Info” block for Optical Reader,
Mouse, touchpad, wifi adapter, speakers, monitor, etc

Scroll down and click on SAVE CHANGES.
==============================================================

Now first thing we need to do is to stop the auto-updating until your problem is fixed.

Control Panel | Windows Update | Change Settings (on the left-side list) |

Set the settings to agree with the snapshot


OK button

I see that I overlooked your SFC question.

Please run 3 times as mentioned in the writeup and then upload sfcdetails. txt

SFC /SCANNOW Command - System File Checker

After and only after you've sent the sfcdetails.txt file then please upload the two files generated by this procedure:

Script:

# ************************************************************
# Places InstalledUpdates.txt on your DESKTOP
# Places NotInstalledUpdates.TXT on your DESKTOP
#
# Hidden updates are ignored.
# ************************************************************

# Start copying with first line that does NOT start with #
# Copy thru 2nd EXIT; 
# Paste into PowerShell using right-click

Try
{
   $error.clear()
   $file = "$env:userprofile\Desktop\InstalledUpdates.TXT"
   If (test-path -path $file) {del $file}
   $update = new-object -com Microsoft.update.Session
   $searcher = $update.CreateUpdateSearcher()
   write-host "`n`n Patience. I'm slowly, but steadily working on fetching the list of installed updates.`n`n"
   $pending = $searcher.Search("IsInstalled=1") 
   foreach($entry in $pending.Updates)
   {
   IF ($entry.IsHidden -ne $true) {
       "Title: " + $entry.Title | Out-file -append $File
       "Downloaded? " + $entry.IsDownloaded | Out-file -append $File
       "Description: " + $entry.Description | Out-file -append $File
       foreach($category in $entry.Categories)
       {
           $d + "Category: " + $category.name | Out-file -append $File
       }
       "" | Out-file -append $file
       }
   }
   If ((Test-Path -path $file) -eq $false) {"No updates have been installed." | Out-file $file} 
# Now to check the uninstalled updates that aren't hidden
   $file = "$env:userprofile\Desktop\NotInstalledUpdates.TXT"
   If (test-path -path $file) {del $file}
   $update = new-object -com Microsoft.update.Session
   $searcher = $update.CreateUpdateSearcher()
   write-host "`n`n Patience. I'm slowly, but steadily working on fetching the list of uninstalled updates.`n`n"
   $pending = $searcher.Search("IsInstalled=0") 
   foreach($entry in $pending.Updates)
   {
   IF ($entry.IsHidden -ne $true) {
       "Title: " + $entry.Title | Out-file -append $File
       "Downloaded? " + $entry.IsDownloaded | Out-file -append $File
       "Description: " + $entry.Description | Out-file -append $File
       foreach($category in $entry.Categories)
       {
           $d + "Category: " + $category.name | Out-file -append $File
       }
       "" | Out-file -append $file
       }
   }
   If (-not(Test-Path -path -$file)) {"There are no uninstalled updates which are unhidden." | Out-file $file} 
}
Catch 
{
   "Unable to fetch update list from Microsoft site"
}
Finally
{
   "End of script"
   EXIT
}

EXIT
EXIT 


# ************************************************************
# Places InstalledUpdates.txt on your DESKTOP
# Places NotInstalledUpdates.TXT on your DESKTOP
#
# Hidden updates are ignored.
# **********************INSTRUCTIONS**************************
# STEP 1 *****************************************************
# RUN PowerShell as administrator
# START ORB | type POWERSHELL | CTRL+SHIFT+ENTER key combo | YES
# ************************************************************
# STEP 2 *****************************************************
# COPY (using CTRL + C) every line down thru both EXIT statements
# PASTE into Powershell by right-clicking at the PowerShell Prompt
# (Ctrl V does not work)
# ************************************************************
# ***************** NOTE - POWERSHELL VERSION*****************
# if you receive this error msg:
# Get-WinEvent: The system can not find the path specified
# you need to update your PowerShell
# you must be using Powershell 2.0 or later.
#
# To determine your Powershell version:
# Run PowerShell
# enter following $host.version
# you should see at least:
# Major Minor Build Revision
# ----- ----- ----- --------
# 2 0 -1 -1
#
# If you do not see the above, update your Vista/Win 7.
# ************************************************************
# *************** NOTE - EXECUTION POLICY*********************
# If you haven't set the execution policy, you may need to:
# Run PowerShell
# enter following without the #
# Set-ExecutionPolicy -executionpolicy remotesigned
#
# ************************************************************

You have two corrupted files for which also the backups are missing:

C:\Windows\"twunk_32.exe"; source file in store is also corrupted
C:\Windows\System32\"QUTIL.DLL"; source file in store is also corrupted

I suspect that my final recommendation is going to either a Repair Install or a Reinstall.

Even a Repair Install is not a painless operation.

In either case, you should backup everything dear to your heart to an external drive.

Supposedly the repair install won't mess up your data files, but...

I'll look at the other two files now.

the other two files are ok.

Here's a link to the SevenForums tutorial on a Repair Install.
Repair Install