Windows 7 Baffling problem with no upload speed on Windows 7

The problem I'm having is that, even though I have normal download speed, my upload speed is almost non-existent. I've been using this custom built PC for about 2 years now. I'm not sure exactly when the problem started either cause for the most part, websites and programs were working (except for the few that required an upload speed like DropBox) and it wasn't until a couple of days ago when I ran speed tests through different websites (speedtest.net, speedof.me, etc.) that I noticed they practically stopped when trying to measure my upload speed (if I leave them long enough, they eventually return with a really low number of just a few Kilobits per second). Although I think the problem couldn't have started any longer than a week ago.

Link Removed
(From Speedtest.net after about 8-10 minutes of waiting.)

Here's the important info about my PC (if there's anything else I need to clarify just tell me):

-Asus P8P67 LE Motherboard (which has a Realtek 8111E Gigabit LAN Controller)
-MSI R5770 Hawk (pretty much an overclocked ATI Radeon 5770)
-Intel core i7 2600K
-3 Hard Drives (C:1TB, D:500GB, E:500GB) (Drive E was just reformatted yesterday)
-Windows 7 64-bit (with Microsoft Security Essentials as my anti-virus)
-SMCWGBR14-N Router (connected to my PC through LAN)

Now here comes the baffling part. I've tried a lot of things to fix it and checked all I can for the cause of the problem and I haven't gotten anything conclusive, but here's a synopsis:

-Other computers behind the same router (wireless and wired, Mac and Windows) are not affected by this problem. They get normal download and upload speeds.
-Bypassing the router entirely, by connecting it straight from my modem to my PC, makes no difference. I still get normal download, but negligible upload.
-Running msconfig and disabling all start up items and services made no difference.
-Starting up in Safe Mode has the same problem as well (at this point I thought the problem was hardware until I tried the next one).
-Running Ubuntu 12.10 through the DVD and running a speed test gives me normal behavior. I get an upload speed of about 5-6Mb/s (so hardware or connection are not the problem).
-Updating Microsoft Security Essentials and checking the entirety of all 3 drives turned up nothing.
-Checking all 3 drives with Malwarebytes turned up nothing as well (just a few false positives, but they're stuff I've had for months and they've never caused problems).
-Deleting the network driver (through Device Manager) and letting Windows reinstall it didn't change anything.
-Deleting recently installed programs and a few others I suspected might interfere with the network (Java, Tunngle, Flash) didn't work either.
-Reinstalling Windows 7 (moving my old stuff to windows.old, but a clean install otherwise) and running the motherboard's install DVD to get the network driver still showed the problem when I first tried it (without updating Windows 7 or the network driver).
-Updating the network driver to the newest one offered by Realtek showed no difference as well.
-Trying to update this new installation of Windows 7 gives me an error (I suspect it's because Windows is having trouble uploading my info and quits before finishing).
Link Removed

-I tried running Ubuntu again through the DVD after all this and everything still works fine there.

I am at my wit's end here, I don't know what else to try. Any help is greatly appreciated.