Hi
What happens if you use the command "arp -a" on the PC when the ping times out
and does the IP of Access point then show up in "arp -a" when you ping from the AP to the PC?
Can you set the access point to a static internal IP and see if this stops the issue as i would imagine the lease on the IP expiring is what causes the issue to come back after a time.
Thanks
Burkem5