IPSec and dead peer detection not working

Hi there,
I have a IPSec VPN between two n0n0walls, one has a static IP address
the other has a dynamic IP address which changes daily. I use a dynamic
DNS provider to track the changing IP number. This works. For the VPN I
use the domain name as identifier. Every night when the IP address
changes the VPN connection is interrupted and does not come back. I have
to manually restart the VPN on the machine with the static interface and
it works. I am using m0n0wall v 1.34a.

I am sure this worked at some stage. Any suggestions what I could look
into?

Regards
magnus