Hhhmmm interesting. Similar problem here although with SBS 2011 instead of SBS 2008. The server was decidedly not genuine and once the admin resolved this he could connect.
Other than that, the only time I've had issues joining computers with the Connect program is when Windows 7 first came out. There was an update rollup that was required to be installed on the SBS 2008 server before it would successfully allow Windows 7 machines to connect.
So in summary:
1) Make sure the SBS 2008 box is activated and genuine.
2) Make sure all updates are installed on the SBS 2008 box.
3) While you are at it, check 1) and 2) for the workstation you are trying to join also.