Hi, I have found an issue with X11 2.3.1 and the pgplot graphing library, which is commonly used by Astronomers. The issue I have is the following, utilizing the "qdp" (Quick and Dirty Plotter) tool as an example. Launching qdp with a sample file works fine. qdp test.qdp To produce plot, please enter PGPLOT file/type: /xs PLT> I get a line plot as I would expected (test.qdp consists of 2 columns of numbers). Now when I try to modify the plot on the qdp command line by, for example the command "ma on" (switch from light to point plotting), nothing happens. In fact all changes to I attempt to make to the plot make no difference, the plot in the X11 window remains static. If I use the "hardcopy" command to create a postscript version of the plot however, the PS version has all the changes applied. I believe that something in X11 2.3.1 has stopped the X11 PGPLOT window from being refreshed/replotted. As far as I know this problem has been introduced somewhere between 2.3.1rc5 and 2.3.1. I've confirmed this behaviour on 2 machines running 2.3.1, including running pgplot from a linux box to a Mac via ssh forwarding, to the same effect. I'll submit a bug. Thanks, Jamie