Norton ghost 15 wont optimize disk space

I have checked the box to tell ghost to optimize disk space and to delete older recovery points automatically to make disk space during disk images but every time I check the status after a scheduled backup for disk images has run they are not run and I get an attention needed because it says the backup didn't work.  I know the backup routine is running as is says it is creating a recovery point set and shows the progresses. At some point it must be stopping , maybe due to the lack of space. Then it just says attention needed.

Any thoughts on how to get ghost to make the space automatically as I thought I was doing in the manage backups section?