This is the second post for the same error:
RMAN-00569: ======= ERROR MESSAGE STACK FOLLOWS =======
RMAN-03009: failure of allocate command on t1 channel at 08/03/2010 19:57:21
ORA-19554: error allocating device, device type: SBT_TAPE, device name:
ORA-27211: Failed to load Media Management Library
First one was about lack of soft links under library directories.
This one is about EMC networker misconfiguration.