One problem that seems to be emerging here is that Channel 6 does not work correctly here. The Laptops see the AP but keep losing the connection. Forcing the AP to use another channel seems to fix the problem.
We suspected this with our old wireless kit but it is easier to diagnose with the ruckus kit.
It may be worth a look on your network. It may not be the the end of our problems, as we are still testing etc but early findings seem to suggest this.