Network problem with 2.6.18-mm1 ?

I am unable to get networking to work with 2.6.18-mm1 on my system.

But 2.6.18 kernel on same system works fine. Here is some info about
the system/debug attempts. Attached are the lspci output and config.

Appreciate any help. Please let me know if you need more info. 

Suka

System info:

	x326, 2 CPU (AMD Opteron Processor 250)

Kernel info:

	$ uname -a
	Linux elm3b166 2.6.18-mm1 #4 SMP PREEMPT Tue Sep 26 18:11:58 PDT 2006
	x86_64 GNU/Linux

	Config tokens differing between the 2.6.18 kernel that works and
	the 2.6.18-mm1 that does not are:

	Tokens in 2.6.18 but not in 2.6.18-mm1 config

		CONFIG_SCSI_FC_ATTRS=y
		CONFIG_SCSI_SATA_SIL=y
		CONFIG_SCSI_SATA=y

	Tokens in 2.6.18-mm1 but not in 2.6.18 config

		CONFIG_PROC_SYSCTL=y
		CONFIG_SATA_SIL=y 
		CONFIG_ATA=y 
		CONFIG_ARCH_POPULATES_NODE_MAP=y
		CONFIG_CRYPTO_ALGAPI=y
		CONFIG_MICROCODE_OLD_INTERFACE=y
		CONFIG_BLOCK=y
		CONFIG_VIDEO_V4L1_COMPAT=y
		CONFIG_ZONE_DMA=y
		CONFIG_FB_DDC=y

	All drivers compiled into kernel in both cases.

Debug info:

	Checked hardware connections :-) 
	(Rebooting on 2.6.18 kernel works - consistently)
	
	$ ethtool -i eth0
		driver: e1000
		version: 7.2.7-k2
		firmware-version: N/A

	$ ip addr
		seems fine (up, broadcasting etc)

	$ ip -s link
		shows no errors/drops/overruns

	$ ip route
		shows the correct gw

	$ ethtool -S eth0

		shows non-zero tx/rx packets/bytes but *rx_missed_errors*
		quite large (~138K) and increasing over time

	$ ping <own-ip-addr>
		works fine

	$ ping <gateway>
		no response.

	$ tcpdump -i eth0 host <broken-host>
	
		while pinging gateway, tcpdump shows messages like:

		18:03:45.936161 arp who-has <gateway> tell <broken-host>

(Config file and lspci output are attached)