A buggy network card forgot it's mac address,
so the XP client asked for a dchp lease with mac address ff:ff:ff:ff:ff:ff

The dhcpd did not notice that the mac address is the broadcat address, and
assigned an IP.
Luckily the network did not went down.

Here are some lines from the log:

Jul  9 15:30:26 s-homoktovis dhcpd: DHCPDISCOVER from ff:ff:ff:ff:ff:ff (ht003) via eth0
Jul  9 15:30:26 s-homoktovis dhcpd: DHCPOFFER on 10.8.48.196 to ff:ff:ff:ff:ff:ff (ht003) via eth0
Jul  9 15:30:26 s-homoktovis dhcpd: DHCPREQUEST for 10.8.48.196 (10.8.48.254) from ff:ff:ff:ff:ff:ff (ht003) via eth0
Jul  9 15:30:26 s-homoktovis dhcpd: DHCPACK on 10.8.48.196 to ff:ff:ff:ff:ff:ff (ht003) via eth0

Powering off the client PC solved the problem :)

Dear submitter,

as the package isc-dhcp has just been removed from the Debian archive
unstable we hereby close the associated bug reports.  We are sorry
that we couldn't deal with your issue properly.

For details on the removal, please see https://bugs.debian.org/1143544

The version of this package that was in Debian prior to this removal
can still be found using https://snapshot.debian.org/.

Please note that the changes have been done on the master archive and
will not propagate to any mirrors until the next dinstall run at the
earliest.

This message was generated automatically; if you believe that there is
a problem with it please contact the archive administrators by mailing
ftpmaster@ftp-master.debian.org.

Debian distribution maintenance software
pp.
Thorsten Alteholz (the ftpmaster behind the curtain)