Thank you for the log file.
This problem appears to have been caused by a spotty connection or a bad DNS server response, which ultimately lead to a malformed path for the Dropbox API. I don't expect this to happen often and should eventually resolve itself.
Let us know if the problem persists and we can investigate further. I will then send you a personal message with instructions on how to enable additional logging and where to send the new log file once the problem has been recreated.
-Jerry