Problems with VT6102 (Rhine-II) adaptors

Hi,

I've recently build a dedicated router box around a EPIA PD 6000E
motherboard (which has two VT6102 Rhine-II ethernet adaptors). It's
got an EPIA patched 2.6.7 kernel on it with a basic iptables NAT
setup.

After a week of use I noticed a rather annoying problem - under load
it will occasionally drop all packets for a few (between four and
five) seconds. This is very noticable when using an interactive
network application (such as ssh) or gaming. Every nine or ten minutes
all net traffic will stop for five seconds and then resume. In between
these outages the throughput is excellent.

Initially I thought it might be a spike in CPU that was killing
iptables throughput. However connecting to the machine locally and
runnig top during the outages showed that, apart from the network, the
machine was perfectly healthy.

Unfortunately I don't enough about the details of Linux network
drivers to debug this myself and so I was hoping someone had an idea
of what to do.

I'm using the standard via-rhine drivers and lspci reports the
following about the card:

0000:00:0f.0 Ethernet controller: VIA Technologies, Inc. VT6105
[Rhine-III]
(rev 8b)
Subsystem: VIA Technologies, Inc.: Unknown device 0106
Flags: bus master, medium devsel, latency 32, IRQ 12
I/O ports at d000
Memory at de000000 (32-bit, non-prefetchable) [size=256]
Capabilities: [44] Power Management version 2

0000:00:12.0 Ethernet controller: VIA Technologies, Inc. VT6102
[Rhine-II]
(rev 74)
Subsystem: VIA Technologies, Inc. VT6102 [Rhine II] Embeded
Ethernet
Controller on VT8235
Flags: bus master, medium devsel, latency 32, IRQ 11
I/O ports at e800
Memory at de002000 (32-bit, non-prefetchable) [size=256]
Capabilities: [40] Power Management version 2

Any help would be greatly appreciated.
vrai.