Rman Backups failed with error code 42 and 6.

Netbackup 7.1

Rman backups used to run fine.  After we migrated our server from Sunfire 6800/6900 to T4-4 (P2V) and upgraded NICs from 1Gb to 10Gb for backups.  Rman backups started to failed with error code 42 and 6.  It is intermittent though.  Some backups are worse than the others.

We implemented a workaround suggested by symantec about using account other than SYS, but it didnt help.

Does anyone have similar issue?  If so, what's your solution?

Thanks