We obviously already contacted Esellerate support, but they haven't replied to us yet. The problem doesn't have anything to do with FSDT, of course, and it affects every other developer that use Esellerate, like FS Labs, FSDG, Flightbeam, etc.
On FS Labs forum, they suggest to use the Google DNS servers ( 8.8.8.8 and 8.8.4.4) instead of your default DNS in the network settings, while Esellerate figures out the problem.