Did your backup suddenly stop going out, around  the same time you recently installed new Virus checking software ? 

Dont forget to allow dataworks to go out to the internet to perform your backups.  Some virus software programs automatically stop all internet access until you 'authorise' programs to access the internet.  If you have scheduled your backup to go out at night, and your recently installed virus

checking software prompted you to authorise dataworks (and you missed it at 2 am in the morning) you might need to go back and tell your security/virus software that dataworks is authorised to access the internet.
Also make sure you do not schedule your virus scan at the same time as your scheduled backup.  Make sure one has completed before the other one starts.