[ale] Static IP became DHCP IP

[JD]

A few weeks ago I brought up an Ubuntu 10.04 server KVM client to run a
Redmine instance.  We use thin as the app server with nginx running on a
different machine doing the reverse proxy and SSL stuff.

I don't have "am-I-alive" monitoring setup yet, so I manually check to
see if the service is working. It isn't quite a production system yet.
Today, nginx said the back end was down.  No ping, no ssh available from
inside the LAN.  Pulled up a console, logged in fine. The static IP had
been changed .. somehow into a DHCP realm.  Huh?  Checked the
/etc/network/interfaces file and it clearly showed the static IP with
all the correct settings. For my sanity, I restarted the networking and
that put it back on the desired static IP, nginx found and started
serving the appropriate pages ... all seems good ....

Except I'd like to know how it got moved from the static IP (verified
working yesterday - had to help an end user login) to the DHCP IP
sometime today.

I've never had to disable DHCP on previous static IP hosts, just
changing the interfaces file has been enough. It appears that the DHCP
client script decided to run and reset the IP address.   The
/etc/network/interfaces hasn't been modified since 10/1 - when the
system was setup. the static IP has been working all this month - no
reboots.

I've checked log files, crontabs, auth.log, dmesg, syslog and don't see
anything funny.

Redmine and thin run as user "redmine" - no privileges and on a high
port.  I've never seen this behavior before.

Any ideas what I misconfigured, if anything?