Problem with Wireless causing Router Resets

Let me first describe my current network setup first. I have the cable modem connected to an SMC router SMC7004VBR (with the newest firmware on their support site) setup as Gateway with DHCP. This router is connected to two desktop computers, as well as the Linksys router WRT55AG version 1 (with the newest firmware available also) setup as Router, DHCP disabled, and the WAN port is unused. So basically the Linksys router is just an access point.

Now I have two older Dell Laptops. One uses an external Linksys wireless card, and the other has internal Intel wireless card and they both work fine with my network setup. It connects to the Linksys router, gets IPs from the SMC router, and both local network and internet works fine. All laptops and desktop computers are running Win XP.

However, recently I've got a new Dell Inspiron 6400 with Intel Pro Wireless 3945 A/G Mini Card. I've installed Win Vista, all newest drivers, and lots of programs. However, I have noticed that when this new laptop starts up and tries to connect to the wireless network, for some reason, it causes my SMC router to do soft reset by itself.

Sometimes, the soft reset would only happen once and the new laptop would get the IP and the network is fine. However, the other times, the SMC router would soft reset, works for about 1 minute, then soft reset by itself again. It keeps on repeating until I power cycle the Linksys router before the SMC router and new laptop would work.

I have tried hard reset both routers to clear all settings to default, no security for the Linksys wireless router, and it is still the same. The only thing I haven't done is reinstall Vista on this new laptop. But I've put a lot of data on the computer that I do not wish to clear it again to do another clean install until it is absolutely necessary. It has to be something about this new laptop as all other Dell laptops I have with Win XP does not have any problem.

Does anyone have any idea what is causing such problem? It is a hassle to keep power cycling the Linksys wireless everytime I want to use this new laptop.

I have an SMC2804WBR. In another forum I found a tip that has worked for me. I disabled uPnP on my router and have had no further reset issues. I used to have reset issues every few minutes whether my new Vista laptop was connected directly or wirelessly. It's been three days now and I haven't had it occur once. I hope this helps!

Eight months later and still no resetting issue! Just for kicks, I enabled UPnP on my SMC2804WBR router and immediately Vista caused my wireless to drop out.

I have a Vista laptop, an old Win2K laptop, and 2 WinXP desktops and with UPnP enabled, the wireless router works fine as long as the Vista laptop is not connected. Had to turn UPnP off again on my router in order to post this message. So far, I haven't seen a solution from Microsoft that works. THIS DOES!