DDNS fails. record allready exists

[magic-bind at damage.devloop.de]

Hi List,
I have not yet found a solution for my problem. So I came here:

I use DDNS. Every night my server (in my local network) is shutting down. On 
the next day I have the problem that DDNS is no longer working, because on 
update I get the error that the DNS record allready exists. What is the 
solution?

I use BIND version 9.7.2_p3-r1.

regards
Daniel