Issue is a result of the a corrupt audit.bin file. To check this, go to:
NV Home directory: NetVault Backup/db
Check the file audit.bin and note the size
The size of this file should not be above the purge limit set in the NetVault Conigurator 'Auditing' tab. If it is, the following problems could be possible:
a) The 'Purge' settings are not working properly
b) The file is corrupt
Audit information could also be generated more than normal, so monitor the growth of the file after the next steps