Did you recently see the new error ‘ORA-15260: permission denied on ASM disk group’ in your ASM administration? Maybe you are still connected as SYSDBA, old habit from 10g?
A quick citation from the Oracle Docs:
SYSOPERprivilege permits the following subset of the
REPAIRoption). All other
DISKGROUPclauses require the
Just connect with
sqlplus / as sysasm
and you are happy.