Problem with my network, PLEASE HELP!!!

Ok. this is the second time I am going to have to call on you all for help.

SPECIFICATIONS
PC: Homebuilt
------MOTHERBOARD:
--------------------------------MANUFACTURER: MSI
--------------------------------SERIES: K7N2
--------------------------------MODEL: MS-6570
--------------------------------VERSION: 1.x
--------------------------------CHIPSET: Nvidia nForce2 SPP
------CPU: AMD AthlonXP 1800+
------BIOS: Phoenix - AwardBIOS V6.00PG
------O.S.: Microsoft Windows 98 Second Edition.
ROUTER:
--------------MANUFACTURER: LinkSys
--------------MODEL: BEFW11S4
--------------DISCRIPTION: an 802.11b 2.4ghz Wireless router
----------------------------------- WITH!!! a 4 port switch.
NIC #1: ON-BOARD NIC, (NVIDIA nForce MCP Networking Adapter)
NIC #2:
----------MANUFACTURER: LinkSys
----------MODEL: WUSB11
----------DISCRIPTION: a software driven, USB NIC that allowes me to
------------------------------- connect to the router via the 802.11b wireless
------------------------------- Network.
------------------------------- Cheap and Functional, but would often cease to
------------------------------- function after extended periods of use, forcing me
------------------------------- to restart.


A fiew days back I took a trip out of town. At one point I called my mom at home and she said the network was doing something funny so she tried to shut all computers down.
When I got back I found my computer stuck at the "Windows is shutting down" screen (Mind you, that it was like this for a couple of days)

None of the computers were able to connect to the router at this point, but after resetting the router, all computers ACCEPT FOR MINE were able to connect to the router and internet.
Mind you that at this point I am using what I listed as NIC #2 (the Wireless USB Nic) to connect my computer to the network.
I attempted to release/renew the IP address, and it did that fine, I recieved a new IP address but was unable to browse (either by IP address OR by URL).
I was also unable to Ping by URL, so I tried manually entering all settings into the Network Stack, INCLUDING, the DNS settings, the Gateway settings, and Forcing a manual IP address.
No effect.
so I tried the TCP/IP Rip/Refresh procedure.
After doing this for the 4'th time (In Safe Mode) I am now unable to even Ping by IP address or URL. But for some reason I am STILL able to recieve an IP address.
AND I am still able to ping the loopback (127.0.0.1) and the IP address I recieved, BUT Pinging the gateway(router) is a no-go.
After many other inovative sollution attempts, I decided to pull out ALL the stops.
I disconnected the Wireless USB Nic (after removing all of it's software) and connected my PC Directly to the routers 4-port switch using a Cat-5 cable connected to my On-Board NIC.
NO-EFFECT.
Still feeling that it was a software problem I dug up an old 10GB hard drive I had. I formatted it, and loaded Windows 98 Second Edition onto it. Then I loaded all motherboard drivers.
IF THE PROBLEM WERE ANYTHING WITH THE SOFTWARE this should have fixed it I assume. But it had absolutely no effect, Leaving ONLY hardware as the possible issue.
I reset all BIOS settings to defaults but that had no effect.
It is still slightly possible that it could be a virus. My virus scan software (PC-Cillin) was inactive at the time the issue appeared. And even after running the scan I realize my virus defenitions are outdated and I am unable to update them.
So I am about to buy another motherboard, before I do I'd like to hear any other possible solutions.
Whoever is reading this,,, If you cant think of any suggestions then I would still be greatfull for an answer to any of the following 3 questions.

#1 I've heard of some viruses that are able to load themselves into your CMOS (or maby it was the Drive cache, Hence question #2). How many viruses are there that can do this??? And where can I find information on them, including Manual detection and Manual removal instructions?

#2 I dont know if my Hard Drive, CD-Burner, or DVD drive have External Cache (I did'nt save the documentation for any of them), How can I find out if they do, and how can I flush it if they do?

#3 if it is truely a hardware problem, how come I am still able to recieve an IP address from the routers DHCP service, and why is'nt anything else being effected?

 

Some of these nVidia on Board NICs are known as troubled. May be you should try to disable it and install regular PCI NIC (they going around for $5).

 

That's probably the best suggestion. but I'm not sure how to go about getting my hands on another NIC aside from ordering it online. and then I'll have to pay S&H costs. There is no reputable electronics store in this redneck town, and Wal-Mart does'nt sell computer electronics, just games. so it's either order one On-Line or drive 200mi to LasVegas. I think I'll order one.
In the mean time, if you can think of anything else, please dont hesitate.