[OS X TeX] Wrong characters in TeXshop editor

[Adam Fenn]

When I type [ in the TeXshop editor I get the character ð and likewise 
þ for /. If I open some of my old files they display the correct 
characters. I've no idea what I've done to mess up TeXshop like this. 
Does anyone know how I can get it working back to normal?

TIA,
Adam Fenn.
 
-------------------------- Helpful Info --------------------------
TeX FAQ: http://www.tex.ac.uk/faq
List Reminders and Etiquette: http://www.esm.psu.edu/mac-tex/list/
List Info: http://email.esm.psu.edu/mailman/listinfo/macosx-tex
List Archive: http://tug.org/pipermail/macostex-archives/
Mac-TeX Website: http://www.esm.psu.edu/mac-tex/