ssh X forwarding not working

So this used to work just fine but I dont know why it doesnt work anymore. I have it all configured in the sshd_config but it still won't even open a connection any more. I can ssh just fine. If I do ssh -X .... it just hangs, there isn't an error or a password prompt. If I try to ssh -X to a host that I havent previously been to, it will ask if I want to save the fingerprint, ask for a password, then hang (once again no errors). Any ideas why this is happening? I need this for work and as I said before, this used to work.