Problem with my net (maybe USB-port-related?)

I’ve recently upgraded my pc (new motherboard, new CPU, new graphic card, new cooler), and since that fateful day I’ve had problems with my internet connection.
The connection will sometimes disconnect, and then I have to pull out the plug to my wireless adapter and then plug it in again. This happens from time to time, but especially when I’m trying to download large(ish) files. Anything less than 50 MB is fine, but any larger and it disconnects. This also happens, if I’m watching long(ish) video clips online. It seems to have a problem with too much traffic.
If I replace my wireless adapter with a cable, connecting my PC directly to the router, the problem disappears. Unfortunately, this is not a solution I can use for more than a few hours a day…
I’m sharing the router with another PC. This one is also using wireless (it’s even the exact same adapter-model), but here there is no problem. Granted, this other PC is closer to the router, and have a slightly better signal strength, but before my upgrade I had no problems at all.
I think the upgrade is somehow to blame; could it be that I somehow messed up connecting the USB-cables to the motherboard, thus making them unstable? I only use my USB-ports for the wireless adapter, and I have no other way of testing them. I’m using the drivers from SP2.

So… Any ideas?

My wireless adapter is a Philips SNU6500, and the router is a Philips SNB6500.

My Specs:

Operating System - Microsoft Windows XP Home Edition
OS Service Pack - Service Pack 2
DirectX - 4.09.00.0904 (DirectX 9.0c)
CPU Type - DualCore AMD Athlon 64 X2, 2200 MHz (11 x 200) 4200+
Motherboard Name - Asus A8N-SLI
Motherboard Chipset - nVIDIA nForce4 SLI, AMD Hammer
System Memory - 2048 MB
Video Adapter - NVIDIA GeForce 7900 GTX (512 MB)
Network Adapter - Marvell Yukon 88E8001/8003/8010 PCI Gigabit Ethernet Controller
Network Adapter - NVIDIA nForce Networking Controller - Packet Scheduler Miniport
Network Adapter - Philips SNU6500 Wireless USB Adapter (192.168.1.11)
USB1 Controller - nVIDIA MCP04 - OHCI USB Controller
USB2 Controller - nVIDIA MCP04 - EHCI USB 2.0 Controller
USB Device - Philips SNU6500 Wireless USB Adapter

Don’t hesitate to ask if you need any other information!

All my drivers are updated... the firmware too...

I have tried moving the adapter (the router is firmly stuck to the wall) but that didn't help. The signal strenght is always next to max (4/5), and as I've said, everything worked before the upgrade (the PC is in the exact same spot).
I haven't got any other cards, but that might just be it; my brother have no problem accesing and downloading from his laptop and my fathers PC works like a charm...
Is there any way to test my USB-ports, if nothing else, to rule them out?

Even if the other PC is using an internal card, you could try swapping them. Also if there is a computer store or big box like Circuitcity or Bestbuy that doesn't have a restocking fee, you could buy a card and take it back if that doesn't fix the problem. I thought I had a bad PSU and bought one from Circuitcity and returned it when I found out it was the mobo and not the card and there was no restocking fee. Don't know what the policy on network cards. If you have updated drivers and firmware and other computers are working with out problems using the same router, it really sound like it's the card. Some devices come with their own USB dirvers but it sounds like you've done about all you can with the drivers, which again makes me think it's the card.

An internal card is one that you put in a slot inside the computer and the antenna sticks out the back of the computer. If the other PC (newer laptops have them built in) has an internal wireless card, just open the case and unscrew it and just put it into an open slot of the other compputer. You'll have to install the driver but it should be on a CD that came with the internal card. If you don't have the driver CD or installation directions, you can always go to the card manufacturers web site in the Support section and download the driver, would likely fit on a Floppy and also should find the instructions for installing, which again is just putting the card in an open slot and when the coputer says New Hardware found, just direct it to where the dirver is, either on the FLoppy or a folder on your hard drive.

hmm odd problem. this probably has nothing to do with it but i was having problems with my wired connection which was to do with my AMD driver for my CPu being out of date. have you updated to the june version. it can be found at AMD's site.

oh and what sort of pings are you getting when it is transferring files.

one last thing is to make sure your securtiy settings are all correct. anf also make sure their is no interference and the signal doens;t pass through anything metal or really thick walls. seeing as how it worked before the upgrade i doub't it is that.

Ok, I'm back! (sorry 'bout the late reply, been on vacation)

I've tried to switch my USB wireless device with my fathers USB wireless device, but no dice.

I've tried to place the USB wireless device in different locations, but that didn't help.

I've also tried updating my AMD-drivers, but that didn't change anything. I did, however, notice, that my RAID controller is unconfigured; could that be a problem?
I've also forgotten to mention, that my PC sometimes (but not always) freezes, when the connection fails (like when I'm in the middle of downloading a large file). I get a message from Firefox, saying that the file couldn't be downloaded, and then the PC freeze... don't know, if that is any help...

Well, I appreciate any tips you guys (and girls) can give me!