DHCP + BIND : DDNS problem

[Jojo]

Hi everyone,

I'm totally new at this and I want to master this. But i have a 
problem.
Running DHCPD and BIND, i can't manage to make dynamic dns work.

I have this setup in my dhcpd.conf (just a excerpt of course ;) :
ddns-update-style interim;


and in my named.conf :
zone "lyon.atempo.dk" {
	type master;
	file "pri/lyon.atempo.dk";
  	allow-update { 127.0.0.1; }
}

The dhcp and dns services are running on the same host.

What I can see in the error output terminal is :

Unable to add forward map from johndoe.lyon.atempo.dk to 
ip.of.john.doe : timed out

Have you got some hints to advice me ?

Thanks by advance, cheers !