Mouse response in Firefox

Perhaps in other browsers? Does that mean you haven't tried it playing in a different browser yet? You really should if you haven't, as if it loads fine in other browsers, it's Firefox that's the source of the problem, not the game. It's important to rule that out first as that can only be done by yourself.

Good thinking, and yes this problem does only happen for me in Firefox, but I can't vouch for others having the problem, hence that qualification. If it doesn't affect anything else in Firefox, then the problem is probably an interaction between the game and the Flash plugin, which operates in a quite different way than in Chrome as you will be aware. Using a different browser is a workaround, though Chrome has many issues of its own at the moment, and this remains a new bug that needs attention regardless.