Same wireless problem happening again

I posted here a while ago about a problem I'm having with our wireless network. It seemed to go away all on its own, but now it's back again.

We have a Dell desktop on the first floor of the house running Vista that is wired to our (brand new) Linksys WRT54G2 router. I also have an HP laptop on the second floor running Vista that connects to the router wirelessly.

Neither computer is showing that there is ANY problem with the wireless connection or internet connection, but I cannot get internet access on the laptop. The Network and Sharing Center (on both computers) shows an "excellent" signal with both Local and Internet access. I am able to view the shared folders on the desktop from the laptop and vice versa, so I don't think the problem is with the wireless signal. It also shows that I have internet access, but upon opening any browser with the laptop, I get "Failed to Connect" error.

I have tried:
1. Restarting both computers
2. Shutting down everything (including modem and router) and restarting it all
3. Resetting the router and going through the setup process all over again
4. Using a static IP
5. Moving the laptop downstairs to see if the range was an issue
6. Using a different router

I don't know what else to try and I don't know what the problem could be; it just came back as randomly as it went away the first time. The laptop is showing that the connection is excellent and that I have access to the internet, but it's still not working.

My ISP says it's not a problem on their end, and it doesn't appear to be an issue with HP, as my friend has an Acer laptop and couldn't connect either. That leaves the Linksys router, but like I said it shows that it's broadcasting the signal just fine and I do have local wireless connectivity so what would cause just the internet connectivity to fail over the wireless but not on the hard wired desktop? Does anyone have any ideas? I'm really frustrated with the whole thing.

 

Check the DNS settings on your laptop. Manually enter the ISP DNS settings.

 

Manually setting the DNS had no effect.

It's sometimes hard to tell if something is wrong or not as the problem seems to come and go every few minutes to an hour. Running a speed test from speedtest.net showed that the hardwired desktop had a download speed of about 24 mbps while the laptop had .9 mbps. Clearly something's going on.

 

Yes, I've tried that... everything appears to be fine, and the problem persists whether I set the DNS addresses manually or not.

The internet works fine on the hardwired desktop, and fine on the laptop if I hardwire it to the modem. The problem is solely with the wireless connection.

But like I said, I can connect to the wireless network just fine, it has an excellent signal, and I have no problems connecting to the local network. It's just the internet that intermittently will go out, but the router shows that it's still connected to the internet so I don't know what the problem is...pages just won't load.

It's not the router, I've tried 3 different ones and had the same problem with all of them. It's not the laptop, as I've had numerous people bring their laptops over and they had the same problem. It's not interference, we've had the same setup for close to 4 years now and nothing has changed - no cordless phones in the way or anything. I don't know what else it could be.