Checking networksettings wouldn't be bad either. Or perfomance for that matter. In the worst case the ISP changed/upgraded/updated some hardware/settings on their switches or routers and cause this. I had the same problem when I was visiting a friend, and went on Second Life. The route taken to the LL servers was bad, and lot's of packets were lost/dropped and this can visualize in either lag or textures/avatars to load extremely slow. Anything else on the internet goes smoothly?