MAC clients (MacBook pro & MacBook Air running Lion OSX) are having hard time staying connected on wireless network with 1142 & 3502 Access Points & WLC running 22.214.171.124 with WPA2 Enterprise for authentication via ACS 5.x. However, Windows clients are not experiencing this issue.
Disable “Client Load Balancing” feature on the SSID configuration. This would solve the above issue for Mac clients as well as few HP & Dell clients. This feature tries to reject the client and have the client try to associate to another AP. In high density environments (with 10+ clients), this feature might cause issues with various devices.
MAC Wireless clients (MacBook pro & MacBook Air running Lion OSX) take a long time (several minutes, roughly 5 minutes) to obtain an IP Address when they first connect in the day.
Try to disable “Client Band Select” feature to see if that helps clients associate better. Depending on the client device, the client still decides what band it wants to use. This feature tries to 'force' devices to associate on the 5 Ghz, but few clients may not connect on the 5 Ghz and prefers the 2.4 Ghz and at times client devices may not get associated because of this feature.
Check if the clients running Intel driver 14.x which has a bug that is resolved in 15.x, try to upgrade client machines to 15.x