Image cleanup error

is no longer available?

You could try the solution/workaround in the following T/N to see if it resolves your issue: http://seer.entsupport.symantec.com/docs/316803.htm

However, having had a further trawl through the T/N's do you use optimised duplications?

The following T/N mentions @aaaab & inabillity to 'clean-up':

A critical issue has been discovered in NetBackup Enterprise Server 6.5GA and higher when performing optimized duplications. Duplications may report as successful, but a buffer overrun can cause an image copy to be created that cannot be restored without a special procedure.

http://seer.entsupport.symantec.com/docs/347220.htm

If this relates, you'll probably have to log a call per the workaround in this document "If a restore or expiration cannot be performed due to this issue, please contact Technical Support, referencing this document ID and Etrack 1977037 "