I've experienced several instances of wireless not being able to connect to my open, unprotected wireless router, but working fine with a password protected one. So far this is more noticeable on Debian based distros.

I was fooling around and installed Semplice on my laptop. When I had to get the firmware working with a broadcom chip, the network would only hook up with my password router. I have a Linksys unit and the one that my internet provider furnished, the providers has the password, and the Linksys, that I use as a ethernet cable junction as well as a wireless box, apparently doesn't "handshake" with the broadcom.

I then ran a Mint live DVD. I had to use a Belkin usb wireless, as Mint wouldn't work with the broadcom. Same thing, protected would establish a connection, open wouldn't. I've had the same thing with Peppermint Linux, and since Peppermint is based on Mint, that's no surprise. I suppose I should see what an Ubuntu live DVD does, but I don't have one handy, although I suppose it would be an interesting experiment.

I bailed on the Semplice install, so this isn't a post asking what I need to do to fix it. Just wondering what causes it. Seems weird to be able to see a network from Network Manager, but not be able to connect to it. I was less than a foot from the router, with the laptop in my lap when I was doing this, and I was just using a spare hard drive to see what would happen, so I know that the wireless hardware is fine, as it works well from the other hard drive (Sabayon).

I am not 100% sure but I believe it is a security setting in network settings.