Wireless Connection Issues with WRT54G + Windows Vista 64 Bit

So I've been having a wee bit of issues ever since getting a new computer with my wireless connection. Previously I had a laptop with a wireless card built in and everything was peachy. I just bought a new desktop about two weeks ago and had a Linksys 54G Wireless card with it. Because it wouldn't install without a special driver [I have Windows Vista 64 bit] I went ahead and found a third party driver as well as one made by the manufactrer of the card [RealTEK I think? I don't remember, it's irrelevant anyhow]. It worked but it had connection issues, I'd get solid speeds but every 10 seconds to a minute or more, it'd cut out for a second or two. Normally I wouldn't mind but it's extremely annoying for games; whether it be old Diablo II or new Team Fortress 2.

I blamed the wireless card at the time since the router I was using hadn't changed at all, so I went and bought a wireless card that actually is made to work with Vista 64 bit off NCIX, the "Gigabyte GN-WP01GS(1.0) Wireless 802.11B/G PCI Adapter 54MBPS". At first it seemed all dandy but I think that was likely due to wishful thinking. Well here I am again, having the same problem.

The router I'm using is a WRT54GS-CA [the CA means it's Canadian]. I've tried updating the firmware for the router and even looked into flashing it with DD-WRT micro but unfortunately the firmware made for the WRT54GS doesn't seem to work for my Canadian version of it despite being the same router. I don't even know if it's the router's fault, it's just the only solution I can think of. As mentioned before,

I've tried changing the frequency from 1 to 6 to 11 to 10 and all over the map. I've tried changing the WEP key to make sure it wasn't someone cracking my key and hogging bandwidth. I've tried power cycling my modem and router a million times, reinstalling the Wireless NIC, doing Windows updates, turning all cordless phones off or changing their frequency; anything that could disrupt the signal. I've scanned for viruses even though I know it wouldn't be them with both Kaspersky and NOD32.

I get a full 5/5 bars on the Vista Wireless thingy [I don't use any third party ones] and it very rarely dips below 4/5 bars. I just tried running a speedtest on speedtest.net and it shows my connection as excellent, giving me 14.5 megabits a second [~1.4 megabytes a second] downloading and about 1-1.3 megabits [100 kb/s] uploading. The ping time to the server about 400 KM away is 23 ms, definitely not a sign of a bad connection obviously. I wouldn't even call it an intermitent problem, the internet only really goes down for about two or three seconds at a time. Either way it's extremely frustrating, especially for games. I know it's ancient but I do like playing Diablo II and anyone who's played will understand it blows dying to something you shouldn't be dying to because a couple seconds of lag.

Any ideas? I understand this is probably a difficult question to answer so I'd appreciate even an attempt at help.