correct me if i'm wrong but the acl applied with this command
"ip nat inside source list 1 interface Ethernet0/0 overload"
should tell the router which interesting traffic to nat. packets that match the acl will be translated, those that do not will just be routed? so what happens if you have that command and do not specify an acl. and you clear all the nat translations. you shouldn't be able to access the internet correct?