I installed your new version 1.4 two days ago. I note that the plugin attempts to create the file and says it is uploading, however there are no new files in the Dropbox folder and no emails notifications to me... here is the latest log file:
04:04:34: Uploading /homepages/13/d445185094/htdocs/wp-content/backups/counting-on-currency-backup-2013-02-13.zip in chunks.
04:04:34: A total of 6248 files were processed.
04:04:25: Approximately 93% complete.
04:04:19: Approximately 93% complete.
04:04:04: Approximately 93% complete.
04:03:58: Backing up WordPress path at (/homepages/13/d445185094/htdocs/).
04:03:58: Creating zip archive.
04:01:21: Your time limit is 600 seconds and your memory limit is 256M
04:01:21: Backup started on Thursday February 14, 2013