If I process the following MWE with pdflatex (TeXLive 2012, Linux)

\documentclass{article}
\usepackage{color}
\def\mymacro#1{#1}
\begin{document}
\pdfinfo{/Title (Some text \textbf{This macro causes problems})}
Hello world
\end{document}

I get an error from ../texmf-dist/tex/context/base/supp-pdf.mkii. That seems to be a ConTeXt file. The error is

! TeX capacity exceeded, sorry [input stack size=5000].
\@@mpstopdf@@unprotect ... \@@mpstopdf@@unprotect
\unprotect \let \@@mpstopd...
l.34     \def\unprotect

!  ==> Fatal error occurred, no output PDF file produced!

It also happens if I load xcolor, but not if I load graphicx or any other package I have tried. While it is not specific to \textbf, I don't get the problem with \mymacro.

What is going on?

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