Online backup hangs at 99% complete

Norton 360 Premier v. 5. When running a backup or system scan, the back up indicator stops at 99% and does not complete. This has occurred several times over the past few weeks. Online backup used to complete 100% previously. Any suggestions?

Norton 360 Premier v. 5. When running a backup or system scan, the back up indicator stops at 99% and does not complete. This has occurred several times over the past few weeks. Online backup used to complete 100% previously. Any suggestions?