So an occasional client has a problem obtaining an IP address from our
m0n0wall dhcp server. I've searched the archives and my problem appears to
be unique in some respects.

Configuration:
m0n0wall version 1.3b1, built Dec 16
1.6 GHz cpu
512 MB ram
reported memory usage: 16%
LAN: nvidia Gbit (nve0) 100baseTX full duplex
WAN: intel pro 1000GT (em0) 100baseTX full duplex

Problem:
We have ~190 client machines/home routers on our m0n0wall lan and from time
to time a client will not be able to get a dhcp lease from the m0n0wall. I
can verify that this has occurred with at least one WinXP client and more
than one WRT54G client. In all known instances the client is not new, and
formerly received an IP address from the m0n0wall dhcp server.

Successful workarounds:
-In some cases multiple attempts to renew over a few hours are eventually
successful. No known explanation.
-Giving the client a valid static IP address resolves the issue and restores
client access to network

Supplementary information:
-Not seeing any cores in /etc or /usr/local/captiveportal
-Not seeing any messages indicating that any log, file system or device is
full
-Unsuccessful attempts to renew a client's IP address do not create any
entries in the dhcp log
-Problem occurs to clients both with and without entries in the dhcp
server's static mapping table

Any insight? If I need to post content from status.php, please name specific
sections, as some of these sections are hugely long and probably not
relevant, I'm guessing, such as "ipnat -lv".