What I expected to happen was...:
I was looking to login to a new server, by entering the domain in the edit server page.

What actually happened was...:
I was unable to complete the process as the page kept 'refreshing' and wiping out the info I had typed. Also, the java window expanded or unexpanded from 'fullscreen' mode unexpectedly.

Steps to Reproduce:
1. Multiplayer Server/Add Server/Edit Server
2. type in Server Name
3. type in Server Address - (in my case play.climaxcraft.com) after a few letters, usually around "play.climaxcra" the bug occurs.

I hope that helps!