This would appear to be a problem with the Vista Security Center, in the same way there was a similar problem with XP's Windows Security Center.
WSC doesn't detect avast! -
http://www.microsoft.com/technet/scriptcenter/topics/help/wmi.mspx#EQKAC. I don't know if this article has been updated to reflect Vista.
Windows XP SP2, Start, Run, type cmd and click OK from the command prompt type 'rundll32 wbemupgd, RepairWMISetup' without the quotes and enter.
This is another solution that works with WinXP, I don't know if the folder structure and services name (winmgmt) is the same.
* Click Start, Run and type CMD.EXE
* Type this command and press Enter:
net stop winmgmt
* Using Windows Explorer, rename the folder %windir%\System32\Wbem\Repository. (For example, %windir%\System32\Wbem\Repository_bad.). %windir% represents the path to the Windows directory, which is typically C:\Windows.
* Switch to Command Prompt window, and type the following and press ENTER after each line:
net start winmgmt
EXIT
Reboot
