Thx for the feedback.
First of all, the first results of my tests are very good. The playlists are awesome!
Here is my IP: 109.190.86.243
This is very specific to developer.echonest.com (API and website unreachable, time out - echonest.com is fine). Of course it could come from my ISP, but I could not easily explain why it is so specific to developer.echonest.com.
Again, thank you for taking care.
Ar.