Hello! Our help will be more effective, if you copy and send us info about your browser and the Savefrom.Net extension: http://en.savefrom.net/user.php?info=1 We'd also need some links you can't download (to test them).
Do you download via the extension SaveFrom.net Helper or the website SaveFrom.net? For the better understanding it'll be great to see a screenshot with the error. We are waiting for your reply, and thank you for contacting us Savefrom.net Team!
Customer support service by UserEcho