I think what happened is that too many tried to claim the heart of the helephant at the same time. You will have to do it again and, next time wait at the heart until the x appears on your screen so you can claim it.
I'm not sure if your computer lags or not. This has happened to me before too. Fortunately I was training my pet, and not in some insane dungeon like Helephant Tower. I did, however, notice that when i hit the x button on my keyboard, I was able to go into the sigil even though the x had disappeared from the screen. I know this doesn't really help your situation, as you will have to do the tower over no matter what. My only other advice would be to contact tech support. I have heard that they sometimes advance people past something if there was a glitch.
