I have a few access points running in mixed b/g/n mode; it seems as though a few windows-based laptops (7,64b) have local network access but internet access is sparse and usually not working (usually cannot ping out to external addresses beyond the gateway). Sparse as in it sometimes will have network access, but likely will drop out in a few minutes, for many minutes. During this time, local network access is fine, I can ping anywhere within the network including the gateway and local dns servers. The laptops are all fresh installs of OS, updated drivers, and one of them is a brand new machine. I have played with settings on the laptops but this does not seem to fix the issue (changed to G mode only, low roaming, disabled bluetooth amp). For some reason I want to think it's a security issue, currently on wpa-psk aes-tkip and I think I'll be soon changing it to wpa2-psk aes only. The access coming and going really makes me wonder what is the problem. The area does have wireless congestion which I plan on making changes to the ap's channels and modes to help. Is this an N-mode issue on the access point? AP model is EAP350. What could be the problem? Why is it an issue of getting out beyond the gateway? This is only, currently, occurring on 3 (newish) of the 70 laptops (apple and windows mixed environment). Other N-devices seem to work fine. Thanks for any help!