I have a similar problem. I just bought by Samsung Galaxy S and and I can't connect to any wifi. The phone is detecting wifi networks, but when I click on my home network and go to type in the password the "connect" button is greyed out - you can't click/tap it. I've tried restarting my modem, I've taken the battery out of my phone and then restarted it, but nothing works.
The very first time I went to type in the password the 'connect' option was available but I typed in the wrong password, and obviously it wouldn't connect. I told the phone to "forget the network" so I could re-connect with the correct password, but then like I said the 'connect' option is now unavailable.
I can't see anyone else with this problem on the forums. So frustrated!!!