If you ever happen to get locked out of a SBS 2008 system, with no way to get back in as Administrator (it's easier than you might think), use the instructions in this blog should get you back up and running.
Note that you will have to have physical access to the server, or else it will be very challenging to solve the problem.
The content of this has been tested for real on an SBS 2008 which had this problem. Check out the bottom of the page for the sources I used to compile this post.

For a background story, read this post.

In order to get in the server, we need some way of an account and password. As the SBS is a domain controller, you can't simply use the local Administrator account...  ...