I have had some issues logging into Heroku using a company proxy; if you are in the same boat, you might want to try the following in Command Prompt:
C:\...\..> set HTTP_PROXY = <your proxy here>
C:\...\..> set HTTPS_PROXY = <your proxy here>
Alternatively, go to your environment variables by right-clicking My Computer > Properties > Advanced System Settings (on the left side of control panel) > Environment Variables.
Create two new user variables, HTTP_PROXY and HTTPS_PROXY.
For these two variables, enter your proxy address. Make sure you add the http:// prefix, or you might get an error when you try to login.
Edit - Since Heroku only uses port 22 for SSH, we can use HTTP-Git and add the --http-git flag to our SSH remote commands. (This is subject to change since this feature is in beta.)
For instance:
heroku git:clone -v -a myWebsite --http-git