I'm getting loads of messages like:

Jun 23 10:24:20 awakening kernel: [ 1691.596823] xt_TCPMSS: bad length (1492 bytes)
Jun 23 10:24:21 awakening kernel: [ 1692.663362] xt_TCPMSS: bad length (1448 bytes)
Jun 23 10:24:21 awakening kernel: [ 1692.663495] xt_TCPMSS: bad length (1448 bytes)
Jun 23 10:24:21 awakening kernel: [ 1692.663588] xt_TCPMSS: bad length (1448 bytes)
Jun 23 10:24:21 awakening kernel: [ 1692.663671] xt_TCPMSS: bad length (1440 bytes)
Jun 23 10:24:26 awakening kernel: [ 1697.062914] xt_TCPMSS: bad length (474 bytes)
Jun 23 10:24:26 awakening kernel: [ 1697.305525] xt_TCPMSS: bad length (1492 bytes)
Jun 23 10:24:27 awakening kernel: [ 1698.946633] xt_TCPMSS: bad length (1492 bytes)
Jun 23 10:24:36 awakening kernel: [ 1707.481198] xt_TCPMSS: bad length (1492 bytes)
Jun 23 10:24:37 awakening kernel: [ 1708.723526] xt_TCPMSS: bad length (805 bytes)
Jun 23 10:24:38 awakening kernel: [ 1709.599461] xt_TCPMSS: bad length (805 bytes)
Jun 23 10:24:41 awakening kernel: [ 1712.211052] xt_TCPMSS: bad length (1492 bytes)
Jun 23 10:24:41 awakening kernel: [ 1712.260588] xt_TCPMSS: bad length (1492 bytes)
Jun 23 10:24:41 awakening kernel: [ 1712.976058] xt_TCPMSS: bad length (1492 bytes)
Jun 23 10:24:43 awakening kernel: [ 1714.225209] xt_TCPMSS: bad length (1492 bytes)
Jun 23 10:24:43 awakening kernel: [ 1714.914961] xt_TCPMSS: bad length (1492 bytes)
Jun 23 10:24:55 awakening kernel: [ 1726.192696] xt_TCPMSS: bad length (1480 bytes)
Jun 23 10:24:55 awakening kernel: [ 1726.192825] xt_TCPMSS: bad length (1480 bytes)

In my dmesg/syslog. This linux machine is among other things used as an internet gateway. Connection is over PPPoE. I have the following line in my iptables script:

$IPT -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu # PPPoE fix

The frequency of this messages increased 10x when I upgraded from Debian lenny with 2.6.27 to squeeze with 2.6.32 few days ago. Why am I seeing this messages and how can I fix them?