The vanishing confirmation box typically occurs because the page hasn't finished loading.

If you still experience problems after letting it load for a bit, could you let me know which browser you are using and if you have any custom CSS, browser extensions / browser addons, or user scripts running from your browser?

That is really odd. Have you noticed any weird problems on other websites you go on? And are you able to try on a different browser, I'm wondering if the problem is related to Chrome somehow...