Note: while the use-case described is about using submodules within a project, the same applies to a normal git clone
of a repository over HTTP.
I have
The above answers worked for me when my proxy doesn't need authentication. If you are using proxy which requires you to authenticate then you may try CCProxy. I have small tutorial on how to set it up here,
http://blog.praveenkumar.co.in/2012/09/proxy-free-windows-xp78-and-mobiles.html
I was able to push, pull, create new repos. Everything worked just fine. Make sure you do a clean uninstall and reinstall of new version if you are facing issues with Git like I did.