Why won't my MacBook Pro connect to Wi-Fi networks that use a sign-in page (captive portal)? Some wi-fi networks require viewing and agreeing to terms before Internet access is allowed.  When my MBP connects to such a network, it attempts to redirect and isn't able to connect. I tried all browsers. However, it works when I boot up Windows on my Mac. Why does it do this? I don't think my /etc/hosts file is messed up. Could anyone give me some insight?

I am using Lion 10.7.2.
I had this problem connecting to the local public library system network. The problem seems to be a result of my having specified DNS servers ((i.e. OpenDNS, Google, etc.)) in my Network preferences. The solution was to create a network location called "No DNS" which doesn't have any DNS servers defined and use that network location when I need to log into these networks.