Hi jvoerman&James,
Sorry for the inconvenience. Our Product Team is actively working on the issue and a fix is being deployed. Here is the latest update of the issue:
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Microsoft is continuing the resolution process for an issue in which some customers are unable to set up or change a hybrid deployment for Exchange Online. Investigation determined that a coding issue caused the hybrid deployment functionality loss. Engineers have developed a fix and are deploying it across the affected environment. The deployment process is taking longer than anticipated and is estimated to complete within 3 days. As the fix is introduced to the environment, users will experience gradual functionality restoration of the hybrid deployment feature. The next update will be provided by March 3, 2014, at 9:00 PM UTC.
Best Regards,
Bruce Zhou