Not sure about the exact cause.
Maybe you did not enter a name in the fields?
Fill ingame-name, then hit uplink, now fill in your registry username and password.
OR registry mail-address and password.
Please check your installed java-version and update if needed. (Java 8u25 is latest)
Your OS maybe also an influence,
if it is anything other than windows 7 or win 8/8.1.
- Andy