1.-Try running sfc /scannow to see if that resolves the issue,
2.- consider going to the secuÑity portal.
1.- Run System File Checker.
press enter and let it scan your system, if any files are damaged or missing
they will be replaced using the files on the windows disk
In Vista run it from an elevated command prompt.
Right click command on start and run as administrator.
2.- Save it, close all windows/programs open, and run as admin.
Go here: Microsoft Malware Protection Center
Click the link in the right frame under ' Latest Definition Updates '
for either the x86 [32 bit] or x64 [64 bit] edition of Windows installed.
*Save* the definitions that will now download.
Once the download completes close all open programs and browsers.
Now run the downloaded file [ if the edition of Windows is Vista, then
*right* click it and choose 'Run as administrator'.
Follow the prompts to allow it to run ].
Did that get the latest defs installed ?