We read this info at a Korean fansite a few days ago but it wasn't confirmed until it was shown on BIGBANG TV last October 5, 2010

From BIGBANG TV:

Quick translations under the cut. (Click)

GD: He was injured while filming

SR: We had a hurdle race and I got injured. Hurdle?

SR: My foot was caught while I was doing the hurdle race. It's a little painful now~

GD: Is this for self-promotion? (joking)

From DCVI: "While filming Enjoy Today, he fell and got hurt. I heard he got onto an ambulance..."

Here's Seungri's injured cut from the episode where they had a hurdle race: (Click)