I have the plugin plus the Zip extension. The zip file is correctly created in wp-content/backups, but the upload to Dropbox does not happen. then the backup seems to cycle endlessly. Log:
09:40:36: There has been no backup activity for a long time. Attempting to resume the backup.
09:34:40: Uploading /home/content/93/8604293/html/rhsquashclub/wp-content/backups/richmond-hill-squash-club-backup-2012-12-15.zip in chunks.
09:34:40: A total of 2033 files were processed.
09:34:35: Approximately 86% complete.
09:34:29: Approximately 66% complete.
09:34:20: Approximately 64% complete.
09:34:11: Approximately 64% complete.
09:34:04: Approximately 63% complete.
09:33:58: Approximately 35% complete.
09:33:52: Backing up WordPress path at (/home/content/93/8604293/html/rhsquashclub/).
09:33:52: Creating zip archive.
09:33:51: Creating SQL backup of your WordPress plugins.