Cant Download Addons!!!!!!!!

Ok so i have downloaded curse slient but i cant download quest helper =[ when ever i click download via curse client it say [cannot connect due to previous nstance error 00000000] Its really angering me can anyone help me. I have vista. if that matters.

Had same issue, anytime I tried to download via the curse client, nothing or some similar error.

No problems downloading and installing manually though.