Wireless network lag spikes

Recently I have been having some wireless network problems, it all started about 2 months ago, but it didn't happen frequently until about 4 days ago, when I'm gaming or just surfing the web at any random time I will just get a huge lag spike that will not allow me to load any pages,if I'm gaming then I my server ping will shoot up very high (4000ms) then it will take 2 minutes or so for it to fix itself,I figured this was a problem with my wireless network adapter so I went out and bought a new one,problem still existed but that adapter wasn't any good so I took it back and bought a better one, sadly the problem still persist.

Some info/things I have tried
I am running Windows Vista 64 bit, I am aware of the fact vista's wireless software scans for newer networks every 60 seconds which will cause a 2-3 second lag spike, however this is not related to my current problem as I have been aware of this for 6+months and have been using a program called "Vista Anti-Lag" which takes care of that.

I connect to the modem/router downstairs from my room upstairs, there is no one on the other computer or on my network besides me, though I have had a family member on the downstairs computer online while I receive the lag spike,he does not experience any slow-down or lag though, just me.

My Wireless Adapter is a Linksys RangePlus Wireless Network USB Adapter
The router I connect to is a Linksys WRT54G.
I have reinstalled the WRT54G software on the downstairs computer,setup a new network with a different wep key, however this didn't help (I also made sure everything was plugged in correctly)
I have tried reformatting my pc,reinstalling drivers,switching USB ports.

My system specs in case they're needed

OS: Windows Vista Home Premium
Memory: 4GB DDR2 ram
Processor: AMD Athalon(tm) 64 x2 Dual Core Processor 6000+ (2 CPUs), ~3.0GHz
HD: 500 gbs

Any help is appreciated very much!

 

DC.FC ... can you tell me more about the regular spikes. I just switched over to Vista64 as a prelude to Win7. Some features are a step forward from XP and some ... well some I just can't figure out.

Specifically in gaming I am getting the regular spikes that you mentioned. Tried Vista Anti-Lag that you recommend and I still have the spikes. What else have you done to eliminate the spikes in Vista 64?

 

I have used the same Wireless Router setup at my location. On the computer that is using wireless do you use obtain ip configuration automatically, or did you designate an ip address to work with your home tcp/ip settings.