Airport Extreme won't update

I have a total of two Airport Extremes (802.11n, 1st generation) and a 1st gen Time Capsule all running version 7.5.2.

I've had an ongoing issue with the two Airport Extremes where they will not update and restart after making any minor change at all. The most recent case is where I attempt to simply add a new wireless device to the "Access Control" table and the base station will not update or restart. After waiting several minutes, I eventionaly have to power it down and back up again. It will come up just fine but with none of the changes I attempted to make. In the specific case of adding a new MAC address to the Access Control table, I've tried it do this both manually and importing the table from the Time Capsule's config file. I've also attempted to make changes both wireless and connected directly via ethernet...no difference.

The Time Capsule updates and restarts perfectly fine while the two Airport Extreme base stations refuse to up update/restart correctly. This hasn't always been the case...this seemed to be brought on with the 7.5.2 firmware update a long while back.

Regards,

Terry