Export: Reset the list of preferred targets

The list of preferred targets needs to be reset for each run of the
preprocessor.

Reported by Bernt Hansen.

lisp/ChangeLog

@@ -1,5 +1,8 @@
 2009-04-19  Carsten Dominik  <carsten.dominik@gmail.com>
 
+	* org-exp.el (org-export-preprocess-string): Reset the list of
+	preferred targets for each run of the preprocessor.
+
 	* org.el (org-refile-target-verify-function): Improve
 	documentation.
 	(org-get-refile-targets): Respect point being moved by the

lisp/org-exp.el

@@ -1156,6 +1156,7 @@ on this string to produce the exported version."
 	 target-alist rtn)
 
     (setq org-export-target-aliases nil)
+    (setq org-export-preferred-target-alist nil)
     (setq org-export-code-refs nil)
 
     (with-current-buffer (get-buffer-create " org-mode-tmp")