My game often freezes in arenas. I am trapped in the arena, everything else stops moving, and I can only move, not attack. However I seem to be actually able to do move and attack, it's just that I can't see it. When I type into the chat it also works. This happens a lot when I am on the final levels of something, so I'm getting pretty frustrated about it.

Is this just a serious case of lag? Or something else?

PS I have problems with attacking sometimes too. When I use the keyboard to attack, it works, but with a mouse/trackpad it doesn't. I'm able to defend during that time though. I am pretty sure it's not hardware problems.