I will have an answer for you in a moment.
Microsoft Security Essentials uses Microsoft Updates (MU) service to deliver the virus and spyware definition updates and product upgrades. The definition updates and/or the product upgrade failures are generally caused by this service and results in a “0x8*******” error. If you encounter these errors, please write down the exact error code and follow these steps.
In Windows XP, click Start , click Run , type services.msc , and then press ENTER.
Right click Automatic Updates and then click Start . If Start is unavailable, click Restart .
In Windows Vista and Windows 7, click Start , and in the Start Search box, type services.msc , and then press ENTER.
Right-click Windows Update , and then click Start . If Start is unavailable, click Restart .
Visit the following Microsoft Web site .
On the "Windows Help and How-to" Web page, enter the error code that you received.
Follow the steps and try again.
To update the virus and spyware definitions, click the Update tab, and then click Update .
To upgrade Microsoft Security Essentials, from the Help menu, click Upgrade Microsoft Security Essentials .
To get support for any issue you encounter with Microsoft Security Essentials, visit the Microsoft Security Essentials support Web site .
In the list of issues, select the issue that is most relevant to the problem you've encountered.
Next, select the type of support you'd like to receive: Community Forum or E-mail Support .
If you think your computer is infected, select the option "I think my computer is infected" and then select Community Forum or Telephone Support .
To connect to the Community Forum, click Forum , and then click Go to the Forums .
To submit a support request by e-mail, click E-mail , complete the e-mail support form, and click Submit .