Actually, I'm getting the same error message when trying to do an import. Can't connect to http://thetvdb.com/api/<apikey>/series/######/all/en.zip in the logs. However, I can browse to the website correctly through a web browser. Just started today, worked fine yesterday.
I have the same problem. But i have the error message "Can't connect to http://thetvdb.com/api/<apikey>/mirrors.xml : Timeout für Vorgang überschritten" in the logs.