The problem in all four cases this year have been because someone treated an SBS server like a Windows Standard Server. And the reality is that while it is based upon standard server, it really is not. There have been major tweaks and adjustments to permit it to work the way it does. Among them is various restrictions on changes to Active Directory. Basically, unless you understand exactly how the SBS Wizards leverage Active Directory, it is best not to do anything through the standard Active Director Users and Computers console. The Wizards require that users, computer and other data are placed in very specific Organization Units, with very specific names. Renaming OUs or moving users into a more “logical” place will prevent the wizards from working properly.
The people who get themselves into too much trouble are often IT consultants who think they know better – but really don’t. The reason is that a newbie administrator will actually read the documentation that comes with SBS and/or pickup a great reference book, which all say the same thing — use the wizards for absolutely everything, don’t make any changes to Active Directory outside of a wizard. The only exception being would be documentation which specifically takes SBS into account. A Microsoft Technet page will specifically call out that it works with SBS; if it just mentions Standard Server, beware! Remember that SBS is made for oranizations of 75 users or less, and in these environments, rarely will you need a complex OU scheme.
In all four cases this year, it has been because someone has renamed or deleted the default SBS OUs which are created automatically. A quick rename of the OUs back to what they were origionally named, will resolve your problems. That’s it, no big changes, registry adjustments, etc. Simply put the OUs back to where they were automatically created and you should be all set.
Remember, SBS 2003/2008 is not Standard Server, nor is it Exchange Standard — it is a (for lack of better terms) hacked version of Server Standard and Exchange Standard – they are ment to be managed nearly 100% by the wizard and SBS consoles.