Japanese 'Yen' Symbol' appearing in place of '\' key

[Monty Python]

I've noticed recently that my version of IE is dsplaying
Japanese characters when they should not be appearing.
For example, the Japense 'Yen' symbol appears in place of
the '\' key in URL's. Some english language characters in
web pages are also being replaced by japanese characters.

Changing the encoding manually in IE fixes the problem,
but reappears soon after if I load another web page. How
do I change the encoding permanently?

Unfortunately, removing Japanese language support is not
an option.

Monty Python