First let me say I'm using windows vista on my own computer for the first time, so please give me a reasonable amount of explanation if it's something confusing with vista.
I just built a new computer and I have a strange issue with my wireless card. I have a ZyXEL M-302 wireless card. When I first booted up the computer I could not connect to my friends network, but I think that's because I couldn't figure out how to let vista connect to an unsecured network (it would ask me if this was ok, connect and then right after it finished it would disconnect).
On the next network (WPA security) I tried it worked perfectly, loaded pages quickly, downloaded updates super fast. Finally when I got it home it's acting really strangely (at least to a noobie like me). I connected to my apartment router and everything seemed fine. I got on vent, started streaming some music at 256kbs, got on aim, and was surfing the web. After 5 or 10 minutes everything started crapping out. I figured maybe it was the router so I went and reset it, no problems for another 5-10 minutes. I ran some speedtest things online and my computer was only getting like .5-1 mbs download, and >.1mbs upload so I got out my old laptop and ran speedtest on it. My old laptop was getting 7-8 mbs download and like .4mbs upload (which is what my cable company is supposed to be providing us). I tried changing the security (i'm not sure why this would matter, but hey WPA worked and WEP didn't seem to, so might as well make sure). I tried resetting the router/modem. I made sure I had the most up to date drivers on their website (2.0 is the newest as far as I can tell). Also when my internet starts to die, I'm still connected to the router and can still change settings, I just can't do anything online. The internet seems to work fine until I start to stream stuff ie phone calls on skype, music (even at 128kbs). For AIM, and browsing it seems to work fine, it also seems to work fine for downloading windows updates and playing Warcraft III (although that's a fairly old game.
If anything isn't clear or anyone has an idea please let me know and I'll try clarify the problem or try your suggestion. Computer specs are below.
AMD PII X4 955 BE
Corsair 750W TX
ASUS M4A79T Deluxe 790FX
WD 640GB Caviar Black
Sapphire Radeon HD 4870 1gig
2x2GB OCZ Platinum DDR3 1600
ZyXEL M-302 Wireless Card
I unfortunately don't have spares of any of those components currently. I had ruled out the network card since it worked fine on a different network. I also had ruled out the router since my laptop has no problems with speed on the same router at the same desk (essentially the same antenna position). If you think one of these is almost sure to be the problem I can try to get my hands on something.
Sounds like your router to me. Vista requires certain feature support such as IPv6 tunnelling over IPv4. I had similar issues as you when I first moved to Vista (Like having to reboot the router every 15 minutes) until I just got a new router (DIR-555 in my case, but just look for anything that says it's Vista compatible - which, by now, they all should be).