Instead of using your ISP DNS service, you can try free DNS services such as OpenDNS or Google Public DNS to solve ISP specific connection problems.
How to Setup in Windows Mac OS X
- Go to System Preferences.
- Click on Network.
- Select your internet connection in your list and click Advanced.
- Select the DNS tab and add 18.104.22.168 and 22.214.171.124 to the list of DNS servers.
- Click OK
For Google Public DNS Enter 126.96.36.199 and 188.8.131.52 in 4th step.