Using remote apps on local X server

[Bob Smither <bob@smither.net>]

This must be a FAQ, but I could not stumble upon a solution.  With other
Linux boxen, I can ssh -X into them, then run X apps on the remote with
local display.  On a newly installed Sarge Debian box, doing this
results in the following error:

  Gtk-WARNING **: cannot open display:

Any suggestions as to why I can't run the remote app and see it locally?

Thanks!

-- 
Bob Smither, Ph.D.                                 Smither@C-C-I.com
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But when a long Train of Abuses and Usurpations, pursuing invariably
the same Object, evinces a Design to reduce them under absolute 
Despotism, it is their Right, it is their Duty, to throw off such 
Government, and to provide new Guards for their future Security.
      -- Thomas Jefferson, Declaration of Independence, July 4, 1776
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