[OS X TeX] LaTeX won't format emph

[Alain Schremmer]

This morning, LaTeX just ceased to format \emph (and, occasionally,  
section titles) until 2nd typeset. Even after that, if I close TeXShop  
and re-open the tex file, the pdf is e.g.

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So far, \emph worked in sserif and \textbf in both roman and sserif  
but now sserif does not work either:

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I am beginning to get worried. It happened a couple of times a few  
years ago but I have forgotten what it was due to---and what to do.

It may have to do with my starting to use of \colorbox{yellow}{blah}  
(but I have used it a lot before without any problem.)

All log is saying is "LaTeX Font Warning: Some font shapes were not  
available, defaults substituted."

I am running TeXLive-2013 with TeXShop 2.47 under 10.5.8 on a Dual  
1GHz PowerPC G4



Hopeful regards
--schremmer