A little late but this what I found:
Check the user that is in the J2EE Config Tool used for connecting to the UME on the ABAP instance.
You can find it in Cluster-data -> Instance_IDxxxxxxxx -> Server_IDyyyyyyyy -> Services ->
com.sap.security.core.ume.service
Key: "ume.r3.connection.master.user" the value is usually "SAPJSF".
Check if this user is not locked in the ABAP instance and the password in key "ume.r3.connection.master.passwd" is correct.
I unlocked the user and started Server0 in the AS Java Process Table and ... Succes!
Cheers!