A common problem involves entering an email address that's not entirely lower-case. Is that possibly it?

Let's not do necro threading - this topic was about an old downloader, not the current one :). Would be great if you could please add your report to this topic and include the exact Downloader version that you're having the issue with (it's in the Setting's window) as well some info on Windows version you're using

PS: Closing this topic