[AUCTeX] preview \cite

[emacs user]

Hi all, I am trying to have \cite commands be previewed, so I can see
the actual reference.  I put in the preamble of the latex file

\usepackage[sections,displaymath,textmath,graphics,floats]{preview}
\PreviewMacro[!]{\cite}

and then I have ... \cite{myauthor}

previewing this in gnu emacs (24.0.50), I get a question mark instead
of the reference.  c-c c-l shows that latex complains about the
reference being undefined.  I tried to run bibtex before doing the
preview, doesn't help.   The reference comes out fine in the pdf file
produced by latex.

any suggestions as to what I may be doing wrong?

many thanks, E