[XeTeX] I found no \bibstyle command---while reading file foo.aux

[brindle at stud.ntnu.no]

I get this error message from bibtex!

The top-level auxiliary file: Thesis_Frame.aux
A level-1 auxiliary file: Chapters/Color-Draft.aux
I found no \bibstyle command---while reading file Thesis_Frame.aux

This is the file I tried to xelatex then bibtex!

\documentclass{PHDNTNU}
\begin{document}
\include{Chapters/Color-Draft}
\bibliography{sample}
\bibliographystyle{thesisstyle}
\end{document}

This is (part of) PHDNTNU.cls

\NeedsTeXFormat{LaTeX2e}
\ProvidesClass{PHDNTNU}
\DeclareOption*{\PassOptionsToClass{\CurrentOption}{report}}
\ProcessOptions
\LoadClass{report}
\RequirePackage{ eepic, epic, xyling, fontspec, xunicode, xltxtra,  
multicol, vowel, gb4e, cgloss5e, booktabs, natbib, fancyhdr}


I tried with report.cls and natbib but still didn't work.  
Color-Draft.aux looks ok to me, but Thesis_Frame does not contain  
\bibdata{sample} and \bibstyle{thesisstyle}. Does anyone know what  
might be the problem or could direct me toward the solution.

Jonathan