This issue may occur if your computer has a catalog (.cat) file that is corrupted. When the Update.exe tool that you use to apply a hotfix or a security update starts, it verifies the digital signatures of all .cat files. If Update.exe parses a corrupted .cat file, you receive the error message that is specified in the "Symptoms" section.
Note This issue may also occur if you download the update package from the Windows Update Web site and if your computer does not have Internet access when you apply the update package. The update package must contact the Windows Update Web site to be correctly applied.
Resolution
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To resolve this issue, follow these steps:
Verify your Internet connectivity. If you downloaded the hotfix or the security update and then tried to apply it, make sure that you have Internet connectivity. If you have Internet connectivity, and you still experience this issue, go to step 2.
Determine whether one or more of the .cat files are corrupted. To do this, follow these steps:
Click Start, click Run, type sigverif in the Open box, and then click OK.
In the File Signature Verification dialog box that appears, click Advanced.
Click Look for other files that are not digitally signed, and then type C:\Windows\System32\Catroot in the Look in this folder box.
Note If Windows is not installed in the C:\Windows folder, modify this entry accordingly.
Click to select the Include subfolders check box, click OK, and then click Start.
All the unsigned files appear in the following list in the Signature Verification Results window:
The following files have not been digitally signed
Note These results also appear in the C:\Windows\Sigverif.txt file that is automatically generated. For an example of a Sigverif.txt file, see the "More information" section.
Delete any unsigned .cat files from the Catroot folder. To do this, follow these steps.
Note This procedure applies only to .cat files that are not digitally signed. It does not apply to other files that are not digitally signed.
Start Windows Explorer.
In the %Windir%\System32\Catroot folder, delete the .cat files that are not digitally signed.