Ok, the problem seems located and handled .... maybe :p
But, unfortunatly, as I have only a FileServe account, it means jDL (my favorite) has to be replaced because no use anymore .... well this sucks. My dowload speed is reduced from 3.3MB to 117KB, and that's not standable.
I hope for jDL lovers, like me, it take no time to repair this problem. In the mean time, I'll use FDM instead of jDL.

note : i've waited 4 days for jDL to get on his feets but no more ^^
note2 : as info, 'FDM' and 'Get Go' managers don't work neither with FileServe (actually it's even worst) :'(