I am working on a beamer presentation which will include many mathematical symbols. I use MiKTeX 2.9 and the TeXstudio IDE.
I have run into a problem when I attempt to use certain mathematical symbols. Here is a MWE:
\documentclass{beamer}
% Document
\begin{document}
\begin{frame}
\begin{itemize}
\item This is normal text
\item This item has a greek symbol: $\alpha$
\item This item uses it as a subscript $C_\alpha$
\end{itemize}
\end{frame}
\end{document}
I use \alpha twice, once normally and once in a subscript. However, this only compiles without the third item. If that is included, this produces the error:
!pdfTeX error: pdflatex.exe (file mathkerncmssi10): Font mathkerncmssi10 at 657
not found
==> Fatal error occurred, no output PDF file produced!
I have made a web search for similar error texts and found nothing. I have no idea how to further proceed, and would appreciate any hints at what is actually going wrong.
Update 1
It seems this is not related to the \alpha symbol at all, but instead just caused by any letters I try to typeset in mathmode. Including
\item $a$
already causes this error and fails to produce any output document.

mathkerncmssiis being called. that may involve looking in your log file and seeing what files are being reported. it's actually likely that it's a composite name, withmathkernbeing specified likeOT1as reported for my attempt; that seems even more probable based on your edit to the question. search for justmathkern; it'll most likely be a slog, but for a starter, it's not in anybeameror "base" latex files. – barbara beeton Jun 15 '15 at 17:02updmapto update your map files. Changing the font like in the accepted answers avoids the error but does not solve the underlying problem. – Ulrike Fischer Jun 16 '15 at 07:12