We have a customer who added a simple date attribute using a SQL command (ALTER TABLE...) to a SQL Server based geodatabase. The column is visible in the SQL or Enterprise Manager interface but does not show up in ArcGIS. Rebooting and re-opening tools does not change the behavior.
SQL Server 2008 R2 and ArcGIS SDE/Desktop 10.1
This is an interesting dilema in that we have other customers who do the same all the with a Oracle 10g R2 geodatabase but their backends are SDE 9.2-9.3 based.
Thanks,
-Jim Fox