Xforwarding question

[Linda]

I am playing around with X11 forwarding.
When I use ssh -X and I am done and exit if I have displayed a remote graphical program instead of exit giving me logout then connection closed then a prompt on the local machine I get a response of logout but no connection closed and have to enter ctrl C to return to the prompt 
I notice the same behavior with Xming and Putty from windows, ie not a clean exit so you have to manually close putty. Just wondering what I need to do to properly close everything when running remote X applications over ssh or putty. 
              Thanks
              Linda