I have two routers running NAT. I replaced a 1602 with a new 2620XM router running Ver 12.3(6b) with the same exact configuration minus no ip route cache on the interfaces and I can ping a destination across both NAT routers succesfully from some IP addresses while others I get 50% packet loss. If I move a working IP address to another PC it works there too. So for example 10.0.0.11 won't work but 10.0.0.10 will. Why would NAT be causing this problem? Is it an IOS issue?
I am attaching the configurations.