Its a really annoying problem – the Wifi works for a lot of laptops but not with others.
The problem we had was with a 2013 MacBook Air connecting to a NetGear WG102 with the latest firmware 5.0.3
A 2012 MacBook Pro Retina and numerous other laptops were fine, but the issue persisted with the MacBook Air.
To solve the problem, we reverted the access point back to 5.0.1 (download only the right version for where you are in the world). All devices can then access the wifi.