cannot scan : error code 0x8007139f

Very strange error for MSE.

Perform these checks, especially theBOLDED ones:

Verify that you have removed/uninstalled all other real-time antimalware products that were ever installed on your PC, including free/trial products that were installed when the PC was purchased (Norton, Symantec, McAfee, TM, AVG, Avast, Avira, Malwarebytes (paid), etc). 

Then, use the cleanup tools here: List of anti-malware program cleanup/uninstall tools If yours is not listed, go to the manufacturer and get it. 

Verify that your PC clock is correctly set (date, time, time zone). If not, correct it.

Verify that Windows Defender is uninstalled (if XP), or Disabled (if Vista/W7).

Verify that you are up-to-date with SERVICE PACKS and updates (including .NET and IE). Yes, it can take some time to do this.

Verify that the Windows Firewall is on, and set to defaults. 

Verify that you are using version 2.0.657.0 of MSE (as of 2010-12-16).

Then, restart your PC.

You may need to remove and reinstall MSE as well. If so, you can use the procedure(s) here to uninstall MSE: Uninstalling MSE. 

Then, use IE or Firefox, and go to www.microsoft.com/security_essentials and click DOWNLOAD. Do not navigate and download via TOOLBARS.

If the problem persists, submit a support case to Microsoft: https://support.microsoftsecurityessentials.com/?scrx=1

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