Wonder if you have a clue because I do not. my other office is Peet's coffee. Three weeks ago I stopped being able to use their wifi. Their pages takes forever to load and then the code submission takes forever and shoes a "can't see this page". I've used the Disk Utility, I've restarted, made sure my wifi is on, the airport was on etc. I cannot get online to any Peets. No problem at any other locations; my local coffee shop, no problem. have any ideas.
What I would try:
1) Open a different web browser such as FireFox,
2) Use a different account (set up a new account for testing if you do not already have one),
3) Make a new network location with default settings,
4) Take your Mac to an Apple Store to test and perhaps talk to a "genius",
5) Go to a different coffee shop.