Cisco Aironet 1140: 3 of our 4 are always hanging

Question

Our office has 4 Cisco Aironet 1140 access points mounted on the ceiling. They are all powered via PoE. Every few days 3 of the 4 access points hang and have to be rebooted. When they hang I am not able to connect to their web interface to check the logs. The fourth, for some reason, always seems to stay alive.
I checked the configuration for all AP's and "Hot Standby" is disabled
They are all using static IP addresses. I've tried 2 different banks of static IP addresses and 3 of 4 still hange so I don't think this is an IP conflict
I have saved the configurations and compared them and they are all identical, where possible.
They all have software version: 12.4(21a)JA1
They all have bootloader version: 12.4(23c)JA1
I have tried to download the latest software/firmware, but unfortunately I do not have a valid service contract in place with Cisco and therefore can't download the latest version. All of our CISCO hardware was purchased from Amazon resellers and they can't seem to help me with this. I have also tried to contact Cisco and they can't seem to help either. If anyone has a suggestion on how I can get a valid service contract that information would also be very helpful!!!
Does anyone have any ideas why 3 of our 4 access points would hang? When they hang, I can't login to the web interface and the logs seem to reset when I reset each access point. I have also set up an rsyslog server and I don't see a log entry that would indicate a problem.
Any ideas?
Thank you

Answer 1

Here is the config for one of the AP's that keeps hanging:
! Last configuration change at 09:18:05 -1000 Mon Jan 30 2012 by admin
! NVRAM config last updated at 09:18:05 -1000 Mon Jan 30 2012 by admin
version 12.4
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
service password-encryption
hostname XXX2
aaa new-model
aaa authentication login default local
aaa authorization exec default local
aaa session-id common
clock timezone -1000 -10
ip name-server 8.8.8.8
ip name-server 8.8.4.4
dot11 syslog
dot11 ssid XXX2
   authentication open
   authentication key-management wpa version 2
   guest-mode
   wpa-psk ascii 7 01234567890123456789012
username admin privilege 15 password 7 01234567890123456789012
bridge irb
interface Dot11Radio0
no ip address
no ip route-cache
encryption mode ciphers aes-ccm
ssid XXX2
antenna gain 0
station-role root
bridge-group 1
bridge-group 1 subscriber-loop-control
bridge-group 1 block-unknown-source
no bridge-group 1 source-learning
no bridge-group 1 unicast-flooding
bridge-group 1 spanning-disabled
interface GigabitEthernet0
no ip address
no ip route-cache
duplex auto
speed auto
no keepalive
bridge-group 1
no bridge-group 1 source-learning
bridge-group 1 spanning-disabled
interface BVI1
ip address 192.168.100.252 255.255.255.0
no ip route-cache
ip default-gateway 192.168.100.1
ip http server
ip http authentication aaa
no ip http secure-server
ip http help-path http://www.cisco.com/warp/public/779/smbiz/prodconfig/help/eag
snmp-server community MyCommunity RO
bridge 1 route ip
line con 0
line vty 0 4
sntp server 192.43.244.18
sntp broadcast client
end