SIOCSIFFLAGS: eth0 not working!!!

I am trying to connect my Linux to a linksys WRT54GS and my Linux is refusing to get an automatic IP by the DHCP server.

I have another linux connected to the same router and is perfectly working.

The error i am getting is:

Bringing up eth0:
SIOCSIFFLAGS: Operation not permitted

What shall I do?

Sometimes at boot time, my Linux is freezes.
It stops at
Bringing up interface eth0:
Determining IP information for eth0...

I have fedora core 6 version 6.2.18 if that is useful.

and... some other time it just says:
[FAILED] after 2 mins

That is really puzzling me