Laptop connects to wifi, but no internet

Well since yesterday my laptop can't really go online anymore, I haven't really done any changes to the router at all, but the laptop kinda just stopped. There's no spyware, viruses or anything. It connects perfectly fine to my wifi, but can't get any website. I've tried disabling WPA, and Mac Filters, and got nothing still getting the Firefox and IE message, Unable to connect.

I'm havng a similar problem.  Recently, a desktop running xp is having trouble retrieving webpages.  It connects to the router fine, and to the internet, but IE and Firefox give the could'nt find webpage error.  Other programs like avg and windows update can download updates without trouble.  I thought it might be malware but, connecting wirelessly using the same usb adapter with a Dell laptop, gives the same errors.  My desktop and my DS conncect fine.