A nohup bug?

Maybe my Unix/Linux is too rusty, but the nohup command seems to be bugged.
I have an ssh session to a remote machine with the DISPLAY variable set to my current screen. I start an X application (e.g. firefox) with "nohup firefox &". If I now exit the remote shell (be it with ^D or exit), the response is "logout"... and nothing happens. That ssh session just sits there, echoing what I type but not doing anything. If I hit ^C, the ssh session terminates but so does the process started with nohup! Surely, that's not supposed to happen!
I have an ssh session to a remote machine with the DISPLAY variable set to my current screen. I start an X application (e.g. firefox) with "nohup firefox &". If I now exit the remote shell (be it with ^D or exit), the response is "logout"... and nothing happens. That ssh session just sits there, echoing what I type but not doing anything. If I hit ^C, the ssh session terminates but so does the process started with nohup! Surely, that's not supposed to happen!