X11 stopped working on OSX

[YC]

I have been using the X11 terminal window, Gimp and IDL for the last 2 years without a problem. Today, all of a sudden, X11 won't open anymore. I click on it , the menu bar appears, and nothing happens when I click on applications/terminal. Then X11 closes or disappears by itself. Any idea what has happened and how to fix this problem? Would appreciate any advice. I am using version OSX 10.4.11 Tiger.

Thanks.