After lucid upgrade, .emacs error loading mailcrypt on 1 of 2 machines

[Adam Funk]

I just upgraded two machines from karmic to lucid.  Both have 

(require 'mailcrypt-init)
(load-library "mailcrypt")

in the ~/.emacs file, and the same mailcrypt and emacs packages
(version 3.5.8+CVS.2005.04.29.1-12.1 and 23.1+1-4ubuntu7) installed.
On one of them, no problem.  On the other, emacs gives this error
(verbose version from the --debug-init option):

Debugger entered--Lisp error: (file-error "Cannot open load file" "mailcrypt")
  load("mailcrypt")
  load-library("mailcrypt")
  eval-buffer(#<buffer  *load*> nil "/home/adam/.emacs" nil t)  ; Reading at buffer position 3202
  load-with-code-conversion("/home/adam/.emacs" "/home/adam/.emacs" t t)
  load("~/.emacs" t t)
  #[nil "…´
  command-line()
  normal-top-level()


Any idea what could be broken on one but not the other?

Thanks,
Adam