Can't seem to NMAP

[j.m.]

I cant seem to NMAP localhost or even my IP address, actually i cant seem to nmap anyone. Response I get is

"Note: Host seems down. If it is really up, but blocking our ping probes, try -P0
Nmap run completed -- 1 IP address (0 hosts up) scanned in 12.264 seconds"

i can still ping anyone and can also be pinged
What does it mean if you cant NMAP yourself or anyone else for that matter?

On RH I could specify my own IP as nameserver then just put in GW address of a router connecting to the net and i could connect to the net and resolve locally. I cant seem to do this on SUSE. If i specify myself as nameserver i cant connect to anything, not even anything on my own pc.

Could there be link between the first query and this one?

[blaqb0x]

have you set you network mask correctly?

255.255.255.0 is what most use.

[j.m.]

Yep everything is set up correctly, but for some reason i cant seem to nmap.

Do you know what this could mean? ( Not being able to Nmap)