Doesn't sound familiar. Can you post a show version? Are you talking about the dhcp settings that the router receives as a dhcp client, or are you using the 871 as a dhcp server and finding it isn't handing its clients dhcp dns information after reload. If it's configured as a dhcp server, please post your dhcp pool config, such as:
ip dhcp pool test
import all
network 10.10.10.0 255.255.255.0
default-router 10.10.10.10
!