SSH Over OpenVPN – Fix SSH Traffic Freezing When Catting a File

I have an openvpn (version 2.1_rc15 at both ends) connection setup between two gentoo boxes using shared keys. it works fine for the most part. I use mysql, http, ftp, scp over the vpn with no problems. But when I ssh from the client to the server over the vpn, weird things happen. I can login, i can execute some commands. But if i try to run an ncurses application like top, or i try to cat a file, the connection will stall and I'll have to sever the ssh session.

I can, for example, execute "echo blah; echo .; echo blah" and it will output the three lines of text over the ssh session fine. But if i execute "cat /etc/motd" the session will freeze the moment I press enter.

I compiled openvpn 2.1.1 on my mac and copied over my config directory from my gentoo client. The mac connected and ssh sessions worked fine without freezing.

I then compiled it on my older gentoo box (2.6.26 kernel) which I am retiring due to a dying hard drive, and ssh over it also works perfectly.

Why does it fail on my brand new gentoo box ? I've tried compiling three different kernels in case it was that, but other than that there should be no difference between my older and my newer gentoo boxes that I can think of.

Any suggestions on what's wrong ?