I am using the commercial fonts "Flexo" and "Brix Slab" with XeLaTeX:
\documentclass{book}
\usepackage{fontspec}
\defaultfontfeatures{Mapping=tex-text}
\setmainfont{HVD Fonts - BrixSlab-Light.otf}
\setsansfont{Durotype - Flexo-Medium.otf}
\usepackage{blindtext}
\begin{document}
\blindtext
\sffamily \blindtext
\end{document}
The generated PDFs look good with every PDF viewer except for Adobe Reader X and XI where the "Flexo" font is a mess.

The output of "pdffonts" yields:
name type emb sub uni object ID
------------------------------------ ----------------- --- --- --- ---------
YCEXOQ+BrixSlab-Light-Identity-H CID Type 0C yes yes yes 5 0
JAZBMS+Flexo-Medium-Identity-H CID Type 0C yes yes yes 7 0
The problem occurs under Linux (TeXLive) as well as under Windows (MiKTeX).
What is the problem?