I would do the following:
1. Turn OFF ALL Devices, wired and wireless.
2. Factory reset the router.
3. Turn ON one Wired PC and go in and see if it's in the Dynamic Clients list, If so, Reserve it, Save settings and reboot the router.
4. Turn on the next device and do the same thing by turning on one device at a time and reserving it and letting the router reboot.
When you get this all done, save the routers configuration to file under Tools/System.
Did you follow the FW update sticky information when updating?