I would reconsider the Lachesis. They are prone to being faulty with the mouse becoming uncontrollable because the cursor develops a mind of its own, jumping all over the place. Google search the problem.
I have had mine just 6 weeks and it no longer works on my Steelseries mouse mat, yet works fine on the desk; weird. Support ticket with Razer has yet to find a solution.
I regret buying this mouse.
You got the latest razer firmware? a new update was released in mid august v1.75