blank page on new .pdf created by new .sty

[Pierre van der Laat Ulate]

My version number is Lyx 1.4.3 on Mandriva 2007
I aded a new myclass.sty and based the layout of article.layout, as explained 
on section "5.2.2 A layout for a .sty file" of the "Personalization" help 
section
My problem is that I may work with myclass, but whenever I try to export the 
document to a .pdf or dvi, I get a "blank page generated message" and an 
error message saying:

"LaTex Error: File 'opex3.sty' not found"

These are the modifications I made to de article.layout file:

# \DeclareLaTeXClass[article, ~/.lyx/layouts/opex3.sty]{article (Optics 
Express)}
Preamble
    \usepackage{opex3}
EndPreamble

Pierre