Can't connect to public WiFi with MacBookPro at coffee shops and libraries

There is a thread on Apple Discussions for this issue: Public wifi hotspot problems.

A suggestion:

Nothing in your MBP is seriously miss-configured. Most times it's the service. What I do is to create a new location for every public hotspot I visit. Outline the preferences along with ISP (network names) in my Preferred networks list.

If a hotspot reacts like the one's that are giving you issues I manually type the hotspots sign-in page in the url address in my browser. Once there I can bookmark that page for the next time it gets buggy.

I had a problem like this getting web access on the guest network while on a recent visit to a client's HQ building. In the end, having tried everything else I could think of, I restarted the machine (2008 MacBook, 10.5.7) after having joined Airport to the network and it connected to the auth page first try. I've no idea why this worked, but it may be worth a go.

Regarding your Parallels superstition, I have VMWare Fusion installed. Might be relevant, might not... hopefully someone else will come up with a definitive answer...

I had this issue with my 2006 Macbook Pro. I took it to an Apple store where I was told it's an internet card issue and they charged me $95 + $85 labor to replace it.

My feeling is the card was defective to start with. I had problems with Wi-Fi from the very beginning.