While I'm not sure if userzoom uses flash, I do know that the issue in flash has been patched. I was having issues loading userzoom as well and I have flash installed.
Reload fixed it thankfully. Does an expiring hit count as a return in terms of locking out? I can't remember.
Try going to the last one in your queue, sometimes when you are adding more they will open up and that will make the last one you added be the next one you can do.
You can use Flash again. They released the update on the 16th. Just follow the link(s) in here to download the updated version. https://helpx.adobe.com/security/products/flash-player/apsb15-27.html
Frogman, I think I might have found the scariest horror ever. Its a documentary, so it being real makes it even scarier. It's called "Jesus Camp" and you might want to leave your lights on.