Here is an article on their blog detailing the events of the 2010 Arabic Festival. An excerpt:
But to take the edge off your curiosity, here are some basics: Paul, David, Negeen, and I went to the festival to see and comment on the situation. Thankfully, we recorded every second of our activity at the festival. At one point, we came across a festival volunteer who seemed to take issue with us simply being at the festival. We could tell he had a problem with us, and so we asked "What are we doing wrong?" He said "Put the camera and microphone down, and I'll tell you." (By the way, there was more to this conversation, but when you see the footage, I think you'll see I'm being fair in my summary.) So I obliged, handing the microphone to David and asking him to not record the man. I then approached him and said "No camera, no mic, tell me what we're doing wrong", he said "Get away from me!" (or something to that effect). Again, I obliged, and walked away.
About 20 minutes later, to shouts and cheers of "Allahu Akbar!" we were all being led away from the festival in handcuffs. From the brief description we were given by the police of why we were being arrested, it sounds like the festival volunteer said we surrounded him and didn't give him an opportunity to leave, thereby "breaching the peace." This is as blatantly false as an accusation can get.