Windows 7 64bit Very Slow Download Speeds

I bought a new top-of-the line HP Pavilion when Win 7 came out - fastest proc they offer, 12GB RAM, Win 7 64bit preloaded.  I've had it about 2 months.  The machine itself is lightning fast - but the internet download speed is molassas slow.  Would be faster to chisel in stone.

My home LAN has the Win7 box, my old HP running Vista (4GB RAM, about 3 years old) and an iMac (4 GB RAM, about a year old).  All 3 machines are connected physically to the router (no wireless connections).  It's a basic and no-frills network - I don't have a webserver, torrents, filesharing or anything like that.  Basic connectivity between machines, and internet access.  That's it.

My ISP is Comcast.

Here are my ul/dl speeds:

          UPLOAD    DOWNLOAD   PING

Win 7   ~3 Mb/s    > 1 Mb/s       88ms

Vista    ~3 Mb/s    20 Mb/s         89ms

iMac    ~3 Mb/s     20 Mb/s        88ms

(this according to speedtest.net)

The upload and download speeds on the old clunker Vista machine and on the iMac are as expected.  The Win 7 box upload is the same as the other machines - the download speed is slooooow.  Less than 1/20th of the Vista box or the iMac.

I also bought a new Linksys WRT210N Gigabit router.  Updated the firmware last night.  Updated the drivers for the Intel NIC in the Win 7 box.  Problem persists.

Rebooted the router & cable model (and the Win 7 box).  Problem persists.

Disabled IPv6, Discovery Mapper - basically everything except IPv4, QoS packet scheduler & file and print sharing.  Problem persists.

Booted into Safe Mode.  Problem persists.

Tried Firefox, Safari, Chrome & IE8 - no noticeable differences.

Disabled Norton A/V, Firewall, Win Defender.  No change.

Swapped the ethernet cable.  No change.

There is only one net device in Device Manager - the Intel 82567V-2  Gigabit NIC.  No conflicts of any sort that I can see.

Ran Windows Update to get the latest stuff - then disabled it.  No change.

Checked all the logs, ran diagnostics, and tried all the "netsh" tweaks I read about.  No change.

So, ultimately, this machine I sunk about $3K into is performing (online) like a snail.  It's almost unuseable, especially since 90% of my job involves online stuff.

I've read dozens - no, hundreds - of similar threads all over the internet, with people reporting the EXACT same conditions - expected upload speed, awful download speed.  So, this is obviously not an isolated problem, and it's not a problem with my ISP, router, modem, NIC, drivers, firewall, A/V or anything else.  It looks like a Win 7 problem - my question is, what is the solution??

Ferris?  Anyone?

Thanks!