Kari (i.e. "Mayhem") sent me more detailed info on watching to the Eastern Regionals on Mavtv for anyone who's interested - here it is:

Go to http://www.mavtv.com/
Click on the blue "Watch MavTV" button which is in the middle of the screen towards the top.
On the bottom of the screen there are "channels" like "motors" and "women." Scroll until you get to"Men's Entertainment" and click on it.
On the right of the screen there is a box with a listing of shows. At the top of the box "schedule" should be highlighted. Click on "Just added" to change the listing.
Scroll down to the bottom of the list and click on the link for "MavTV Roller Derby: Atlanta vs. Windy City."
Enjoy!

This is also posted on her blog