The infamous Skele DC.

I have also been disconnected at random at the regular skele map and at the skele mini dungeon. I -think- I was using Blizzard (as in the sniper skill, not the IL archmage one) at the time of the disconnect, but I'm not sure. It's happened more than a few times though, always at the very bottom of the map.

EDIT: As far as I remember, I think it's happened both on XP and Vista.