We believe that either the installer that you downloaded is corrupt or you need to update the root certificates on your Windows 7 computers.
The latest product release is 2.2 update 1 and the version that you are trying to install is 2.2 GA.
I would recommend that you download the 2.2 update 1 version from the supportline prodeuct updates site and try installing that version on your systems.
If you get the same error then you will need to update the root certificates on your systems.
In Windows 7 this can be done through Windows Updates.
Are your machines up-to-date with all available Windows Updates?