RMAN backup error

Any inputs on below error pls

Starting Control File and SPFILE Autobackup at 30-SEP-2013 02:23:38
released channel: t1
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03015: error occurred in stored script backup_al_all
RMAN-03009: failure of Control File and SPFILE Autobackup command on t1 channel at 09/30/2013 02:28:27
ORA-19506: failed to create sequential file, name="c-3439407214-20130930-ff", parms=""
ORA-27027: sbtremove2 returned error
ORA-19511: Error received from media manager layer, error text:
   ANU2614E Invalid sequence of function calls to Data Protection for Oracle



Best regards,
Vishal