Hello 

I tried to use the function as mentioned above, but obtained
the following error whose but trace I attach. 

I looked into the code (org.el) and indeed it has 
a it has 

(if (featurep 'xemacs)
                  (font-height (get-face-font 'default))

Now the function `get-face-font' is not defined in Xemacs
21.5.29 nor in 21.4. (I shall send a copy to Xemacs beta.)


One remark: I thought that (X)Emacs could not surprise me
any longer since it is such a mature product, but first
org-table surprised me since it brought spread-sheet
features, now org-preview-latex-fragment brings  (X)Emacs
closer to a word processor. Thank you Team!!!!!


Uwe Brauer