On one of my sites that uses this plugin there is an error in the file list. It shows wp-admin then below that shows:
Fatal error: Allowed memory size of 41943040 bytes exhausted (tried to allocate 4224 bytes) in [I excluded the root for this post]/wp-content/plugins/wordpress-backup-to-dropbox/Classes/class-file-list.php on line 111
I have also noticed that in general the file list is a bit choppy and sometimes seems to select and deselect items that I did not click. Might be unrelated, but figure I would mention that as well....