/lib/udev/net.agent causing high CPU usage

We have a number of Soekris boxes running Debian Squeeze. They were installed through an automated process consisting of using deboostrap and copying it unto a Compact Flash card. We use puppet to manage the configuration of all these boxes.

Before Debian Squeeze, they were running Voyage Linux which is just a "lighter" version of Debian. Since we have switched, we're seeing the /lib/udev/net.agent process take up an aweful lot of CPU. We have so far been unable to find any clue as to what this really does and why it's taking up some much CPU time.

In htop we see the following :

We are seeing absolutly no syslog messages related to this process so we're a bit lost... So, I am looking for pointers as to what this process does in general and what could be the potential cause of such CPU usage.

EDIT :

My /etc/network/interfaces is the following :

auto eth0
iface eth0 inet dhcp
       up iptables-restore < /etc/iptables.conf

auto br0
iface br0 inet static
       address 192.168.51.1
       netmask 255.255.255.0
       network 192.168.51.0
       broadcast 192.168.51.255
       bridge_ports eth1 eth3

EDIT2 :

After doing a bit more investigation, this issue only comes up after somewhere around 6 days and is solved for another 6 days by just rebooting the system. Now it makes even less sense. I would like to avoid scheduling a reboot every few days as this doesn't sound like a decent solution.

EDIT3 :

This doesn't seem to happen on a regular frequency as it just happened after 3 days.