Some scenarios can contain a lot of information. The process of entering the ring is not altogether intuitive and can cause some problems. Due to the loading time, moving around before things are fully loaded can sometimes result in the dreaded "Stuck Ring Syndrome".
With that in mind, wait for the scenario to fully load before doing anything. The process should go something like:
1) Join the Ring scenario.
2) Game loading screen shows while you connect to the Ring.
3) Scenario land loads, but scenario entities and logic are still loading (here is where it's important to wait).
4) Game loading screen appears again and a message displays what Act your are entering.
5) Scenario land shows again and everything else finishes loading.
6) Now it's time to play.
If you do happen to get stuck in the ring, I have posted a process to free yourself here:
I hope this helps folks to have a better Ring experience.