Studio 1555 won't communicate with Netgear ReadyNAS Duo

Last week my Studio 1555 laptop was delivered. Setting up the (wireless) internet connection was easy, it al works flawlessly. Then I tried to hook up the laptop to our Network Storage (ReadyNAS Duo - connected through the same wireless router as the internet connetction) en things started going wrong. The laptop 'sees' the network storage, I can open the top folder, but when I want to access the content the whole system blocks. Windows Explorer times out and stops responding. And sometimes even my taskbar dissappeares.

I tried practically everything, from restoring the factory image to a completely new installation of Vista and all the drivers, but the problem keeps ocurring. I tried changing firewall and other protection settings, tried changing the workgroup but nothing works. Since with my other laptop I have absolutely no problems accessing NAS from the same location and when I connect a wire between NAS and my Dell-laptop it all functions perfectly, I'm starting to think there might be something wrong with the laptop. But what? Does someone have a clue?

I tried contacting Dell-support, but when I give my Servicetag, it keeps on saying I have a wrong tag. Even though this is what my sticker says and what comes up when I do the automatic system check.