Laptop WiFi Connection fails

Laptop cannot get any IP address on the wireless adapter; previously connected via both wired and wifi.
AlwaysResolved by toggling or turning off/on the wifi switch of the laptop.

Windows XP, Windows 7

Checking the AP and/or WLC shows authentication failure due similar to below:

Mar 12 06:54:04.731: %DOT11-4-MAXRETRIES: Packet to client ABCD.EFGH.IJKL reached max retries, removing the client
Mar 12 06:54:04.731: %DOT11-6-DISASSOC: Interface Dot11Radio0, Deauthenticating Station ABCD.EFGH.IJKL Reason: Previous authentication no longer valid
Mar 12 06:54:04.738: %DOT11-4-MAXRETRIES: Packet to client ABCD.EFGH.IJKL reached max retries, removing the client

This happens usually during the following situations:

1. laptops go back from standby/hibernate mode;
2. when laptop is using both wired and wifi connections then disconnects from wired; or
3. combination of above both situations.

Resolution:
Change 802.1X Authentication to use 'user authentitcation' only. Computer authentication uses only the cached information which maybe stale, inactive, and/or expired. Specifying user authentication forces the laptop to re-authenticate with the authentication servers -- essentially 'refreshing' the authentication information.

Note that this may not apply to every office network.