Hello, very similar problem here. I bought a Lenovo ThinkPad E330 with a Centrino N 2230 card, and it connects properly to various wifi networks (full signal, even checked the signal quality with inSSIDer) but it just drops the connection even if I keep it right next to the antenna. Sometimes I manage to load a webpage or two but after a couple minutes invariably the browser hangs and can no longer connect to any server, although in the Windows taskbar the network shows up as excellent.
I've reinstalled the Intel drivers and software (downloaded the most recent package on the intel website), deinstalled the Lenovo network manager bloatware, tried various networks and the problem persists.
Currently I cannot use my computer due to this issue.
(Windows 7 64 bit, driver v 15.4.1.1)