I am sorry to post on someone else post.
My ticket was opened on march 29th at 10:59 under "Download issues" on this forum. However since this morning, I was able to download 3 files of 200+ Mb. Changed nothing. I checking bigger files now.
As a comment to help Daltoneb who seems affected by a slow line like my terrible rural line. This problem only occurs on a premium account. I did several traces and they had always time-out after entry "reliance-mrs.cdn77.com [126.96.36.199]" regardless of the ISP used.