I'll try to give as much info as I can but I'm not an engineer for our network. We have the AIR-AP1030-A-K9 access points in our environment. We also still use hard wired jacks as well. Some users running Windows Vista randomly drop the wireless connection. Multiple models of laptops, problem never arises anywhere outside our environment.
We're running WPA (WPA Enterprise in Vista) and TKIP. The access points are connected to Cisco switches. This wireless setup works flawless in Windows XP. Users get 5 full bars of signal, most Vista users have no problem, it's just a handful and it appears to be completely random.