I logged into the admin console by using the “manage account” link displayed in the settings tab of the CrashPlan PROe desktop app. that link logs you right in using an authentication token instead of going through a login prompt.

Once I was logged in to the admin console (as the normal non-admin user that I use to backup my own computer), I used the logout link on the admin console, and strangely enough I was presented with the normal user+password login screen instead of the problematic “Create your admin account”. I logged in with the global admin account and all was fine again.