Update:  The issue with new OverDrive account creation has been resolved as of 5:15 PMUS Eastern Time. 

This message was sent by OverDrive Partner Services last night at 6:43 pm:

Beginning at 5:51PM US Eastern Time, users seeking to create a new OverDrive account are experiencing delays or interruption of service.  We are actively working to resolve the issue and will provide an update when available. 

We have not received verificatio nthat the issue is resolved and will provide an update as soon as we know more.