Sounds like the scroll wheel is wearing out, my 2 year old DA has a pretty loose scroll wheel that randomly scrolls on its own. There's not much you can do to fix the DA's scroll wheel, it's a different kind of design that's not easy to perform maintenance on.
The only things I could suggest would be to either get another DA, or try something like the EC1 which has a pretty similar shape as the DA with a more durable scroll wheel.
Here's a thread with some information: http://www.overclock.net/t/1169826/deathadder-be-loose-wheel