I came across this error on a Small Business Server 2011 installation once or twice where it would error out towards the end with a Target Invocation Exception.

This so far has been identified as using a reserved login name for SBS 2011. Normally “Administrator” and “Network Administator” are reserved, and the installer will not allow you to use those names when creating your first admin account. It will not block you from using “networkadmin”, which is another reserved account. Because it does not block you from doing so, and you set credentials for it, when it comes to installing the Sharepoint portion of the setup, it will fail because it does not have the correct built in credentials, it will have the credentials you set for your personal admin account.

The ONLY fix (and easiest) is to reinstall from scratch, but use a different user name for your administrator account.

This was reviewed and identified here:

http://social.technet.microsoft.com/Forums/en-US/smallbusinessserver/thread/714592ba-a92d-47d7-b961-4e1074b82697/