Getting enough lag even on the game's best settings to make it impossible to get 1000 on hard. Chrome improved things a little bit over Firefox, but did not take away the issue. Windows 7 Home Premium 64b on a HP Pavilion g6. 1.9GHz AMD processor and 4GB of ram.
I found a problem. When two aeronauts attempt the "Cavern Climb" co-op, they come across a room with two switches to control portable ether units. Only issue is that aeronauts can't trigger them, the landscape is in the way!