Symptom:
The AP will show Green light but just stops client connections. Only reboot solves the issue. After a reboot , it allows client connection and light turns blue.You can see below logs in the AP:

*Mar 13 13:34:10.291: capwap_ap_mgmt: Unicast DOT11_ACTION_CHAN_SWITCH_ANNOUNCE
*Mar 13 13:34:10.643: capwap_ap_mgmt: Addr b878.2e7d.8f4f is NOT Blacklisted in Bkt 57
*Mar 13 13:34:10.643: capwap_ap_mgmt: recv auth req from b878.2e7d.8f4f, bssid 003a.9aab.776f, algorithm 0, seq 1,wlan 1, vlan 1 on Dot11Radio1
*Mar 13 13:34:10.643: capwap_ap_mgmt: sent auth resp to b878.2e7d.8f4f, bssid 003a.9aab.776f, status 0, alg 0 seq num 2
*Mar 13 13:34:10.643: capwap_ap_mgmt: forward mgmt frame (0x0) to reap
*Mar 13 13:34:10.643: capwap_ap_mgmt: delete central info of mn b878.2e7d.8f4f
*Mar 13 13:34:10.643: capwap_ap_send_dot11_assocreq:
*Mar 13 13:34:10.643: capwap_ap_send_dot11_assocreq():1452:: assreq->seq_num:0x1
*Mar 13 13:34:10.643: capwap_ap_mgmt: Unicast DOT11_ACTION_CHAN_SWITCH_ANNOUNCE

Conditions:
There are no special conditions.It happens randomly.