Ive been having this same issue for well over a year, ive been trying to open a ticket for weeks to try finally get it fixed but i cant even get a ticket opened 
i not not using prox or vpn or anything of the sort. i have tried on multiple pcs and multiple internet connections and get the same issues no matter what. would really like a fix i find it unacceptable to be unable to play a game i have paid for not to mention bought like 6 sets of d2 cdkeys over they years. i now use my diablo 3 collectiors ed copys of d2 and d2 lod. im sorry but blizzard support has really gone down hill ive been buying blizz games since warcraft one and had active WOW accounts since 2004. i had 2 active subs my gfs and mine. but once again my gf had issues and we went round and round trying to get it sorted and eventually just cancelled both our subs because of bad service. dunno why i am even bother i know as always ill be let down and continue not being able to play the game i paid for.