I've used WordPress Backup to Dropbox on a lot of sites, and it has been woking just fine, but I have one (important) site, where the plugin broke in some strange way.
It happened after a backup-cycle, where it went to 99%, and then stopped/never finished (it stayed on 99% for days). I then stopped it manually and after that, I haven't been able to start it again. You can see a video of the problem here: http://cl.ly/2L0d1v433k0p
I've tried to:
Unlink dropbox accont and re-link
Deactivate the plugin, delete plugin data and files, reinstall plugin
Delete backupfolder in dropbox
Change subfolder in where to store backups
Exclude all but one file (robots.txt)
Update to WordPress 3.5.2 (from 3.5.1)
Info about my setup:
WordPress Backup to Dropbox version 1.5.5
Wordpress version 3.5.2
PHP version 5.3.19
By the way cron is working fine elsewhere, and I have tried:
<Files "wp-cron.php"> Allow from All Satisfy Any </Files>
I really hope you can help...