I have just resolved a similar problem after installing fc10.
It seems that the Network Manager causes resolv.conf to be clobbered when no DHCP is available. NM is supposed to update resolv.conf if the ifcfg-eth0 contains directive PEERDNS=yes. When DHCP tells it what servers to use, it uses those. If DHCP is unavailable NM reads ifcfg-eth0 for DNS directives and uses those instead. If no DHCP and no DNS directives are available then the update of resolv.conf should not take place - but it does, placing null values for DNS into resolv.conf.
I fixed this by writing DNS directives into ifcfg-eth0. I suppose equally one could block all NM activity with NM_CONTROLLED=no, or you could block updating resolv.conf with PEERDNS=no. I did it my way so that I could easily use DHCP when it becomes available.
On FC10 if, you have not set up any named network configuration profiles, the files read by NM are in /etc/sysconfig/networking/profiles/default/
Last edited by steve_s; 05-08-2009 at 07:01 AM.
Reason: improved clarity