This usually happens if the install file is out dated or was corrupted during the download. The first step to resolve this problem is to re-download the file and try to install again. If the problem persists do the following:
- Download our certificate from here
- As Administrator, right-click on the saved file (StartCom.cer) and select 'Install Certificate'
- When prompted click Next
- When prompted select the option to 'Place all certificates in the following store'