Wi-Fi Through Captive Portal Does Not Connect

I have a Macbook Pro running OS X Yosemite 10.10.2. My university uses a captive portal to connect via Wi-Fi. I was able to connect and log in just fine, but after I updated from 10.10.1 to 10.10.2, I can connect and get a valid IP but I cannot access the log in page through the captive portal. When I try to display the log in page from the browser (I have tried Safari, Firefox and Chrome) the result is the same. I get the server not found error on the browsers and the website couldn't be loaded error on the captive portal.

I am able to connect and login to the network using my iPhone and I can connect to other networks from my Mac. Manually deleting the network configuration files and resetting DNS did not work.

I hope there is a way to fix this. Thanks in advance.

ps. I use a MacBook Pro with Retina display, OS X Yosemite (10.10.2), 15-inch, Early 2013