ndis.sys consuming 20+% CPU, going nuts trying to fix

I've been having this problem off and on since I installed W7 that my CPU is spiking during low network use (e.g. 2-3mbit/sec).

My setup is W7 (32), Core 2 Quad Q6600 @ 2.4 ghz, Asus P5E-VMDO, 8gb memory.

Network Adapter is an embedded Intel 82566DM-2 Gigabit. No other network adapters are present. If I disable the adapter, the problem goes away.

Upon further inspection using Procexp I narrowed down the cpu spike to ndis.sys

As an example:

Downloading a file at 300kbytes/sec will spike the ndis.sys process to 16-20% of the total CPU. It will actually drag the computer to the point where a video playing will stutter.

The program I use to transfer data doesn't matter (obviously considering disabling the network adapter resolves all problems)

The start address in procexp is "ndis.sys!Ndispacketsize+0x201f"

As soon as the download is complete the total CPU use with regular network "chatter" (total of maybe 100kbit/sec) drops down to between 1-3%.

So the question is, why is the CPU spiking?

First obvious question I would have is, "Is the driver correct?". Well, it's the driver that Windows 7 went out, found, and installed, so I presume it is. The driver is a Microsoft driver Version 9.13.4.10 dated 03/26/2009 and it is the "latest" driver (e.g. an effort to update the driver says I'm using the latest one).

I have turned off all extra settings including WOL and Power Management.

I have not hacked or tweaked with the network settings nor do I run any software that tries to optimize or hack network settings.

Any ideas? BIOS issues perhaps?

It occurred to me that perhaps this was a rootkit but at this point I've scanned the system enough times (with enough programs) that I doubt this is the case.

Thanks!
Mike

As I indicated in my post:

If I disable the adapter, the problem goes away.

Thanks.

whs said:

As a test, shut off your internet connection and work off-line. Does it still spike?

Solved. Overheating CPU. Makes perfect sense.