Windows 7 internet connection is suddenly very slow

++Fixed, see final post

I've been using Win7 for about 2 months now, and all has been going well until 2 nights ago. I noticed that my browsing speeds were very slow, so I just assumed it was my network, and went on about my business. Tonight I fired it up, and ran into the same thing.

I rank the Speakeasy speed test, and my download speeds were only at 300kbps on a 5mpbs line. I started doing some checking on my router, modem etc. and then I had the brilliant idea to run the same test on my laptop running Vista. No problems there, got a full 5.2mbps download. So, I think that rules out anything with my ISP, modem, router etc.

I've uninstalled and reinstalled my wireless network device drivers, changed my auto tuning settings at the command line, turned off the firewall on my pc, closed all unnecessary processes (there's not much on here, fairly fresh install), restarted, held my breath, tweaked settings on my network card, but nothing seems to be improving. This is consistent across Chrome and IE8.

I've been reading through other posts about the same sort of issue, but I haven't come across anything that works. I don't have any AV software installed (I like to live on the edge) but I did run a spyware scan and it came up clean.

Any other ideas? I run a small website business out of my house, and it makes times pretty tough when it takes forever to connect to anything, and then to upload any files. I've wasted an entire evening trying to come up with a solution. Any help is appreciated.

Other information that might be of use:
OS: Windows 7 64bit
Intel i7 860 chip
8gb RAM
Plenty of disk space
802.11n Ralink PCI network card

The trouble shooting continues tonight:
Verified I have the latest firmware on my router (Linksys WRT54G)
Tried installing another USB wireless adapter (Belkin 54g), couldn't even get it to work after completely disabling my other adapter

Next step I guess is to get a really long wire and connect directly to the router.

I don't believe this is the problem, but my router is a Linksys Wireless B/G, and my network card is a Wireless N. Just thought I'd throw that out there, I'm pretty sure I read that it was backwards compatible.

This may help

Why is my Internet connection so slow?

Thanks, but that was actually the place I started.

Turns out it was the drivers for my network card (Ralink Technologies 2860p wireless N) Tried multiple sets of drivers, but the only ones that worked were the ones that originally came with the card on a disk (which I threw away)

Anyway, that'll be the last time I listen to a salesperson and buy anything other than a Linksys product when it comes to networking. Picked up a new card last night, swapped them out, and I'm back up to full speed.