I'm going to suggest that you do a web search for "join linux pc to windows domain."
It will turn up a number of resources. One of them might speak to your situation.
For more help, it would be useful to know more about what distro/version of Linux you have installed and how the Windows domain is structured and about your proxy settings.
Is the domain using Active Directory (I suspect it is) and so on (it's been so long since I've been in a Windows Domain environment, I don't even know what questions to ask)?