I must say this scares the day lights out of me. I can't see the web cam, so I don't know what is going on. I had a friend lose a mare and foal just a few weeks ago. Similar sounding situation....
She was going out checking on the mare, found her down and thought cool here we go. Well the mare couldn't get up so she called her vet. He was out on another farm foaling out a mare. When he still hadn't arrived a few hours later, she called him back to remind him to GET THERE. The mare didn't seem in pain, she just couldn't get up. Suddenly she started screaming and thrashing then dropped over dead. The vet arrived about 10mins later. He figured the foal was turning and started tearing the uteres away from the cervical rim. Figured this had caused the mare to be unable to get up, due to the nerves running right through there. Then it turned some more ripping away and the mare bleeding out almost instantly.
I hope this is NOT the case with your mare and we will hear good news soon!