why won't my laptop connect to a wifi connection

I travel a lot, and many times there will be a good wifi zone. My laptop will recognize it, and even connect to it, but won't function.

I'll log off, delete the connection.....re-connect, and still the same thing.

Then I can go to a coffee shop next door, and the connection will work.

This is location dependent.

I check my security settings, but can't find any check box or setting that controls this.

Other times, I can connect to a wifi zone, but my VPN won't work )usually meaning the wifi connection is weak).

please help.....I am in a coffee shop now with a friend who also has a macbook pro, yet her wifi connection works well.

(the connection to my phone also works well.)

thanks,