Have you tried redirecting your DNS queries to different servers?
You could try using Open DNS servers:
208.67.222.222
208.67.220.220
Even if you have a dynamically assigned IP address, you can manually specify the DNS servers your PC points to.
Also, check your local HOSTS file to make sure nothing suspicious is going on there.
I thought about using different DNS servers, but ruled that out after mobile data on T-Mobile had the same result.