Accented character not displaying in some fonts

[John Talbut <john@dpets.demon.co.uk>]

I am having trouble with the displaying of some accented characters. á and ó 
appear wrongly in regular Arial and Bitsream Vera Sans fonts.  In both the á 
comes out as a space.  In Arial the ó comes out correctly but in Bitsream Vera 
Sans the ó comes out as Û .  If any effects are applied to the characters (bold, 
underline, italic) they display correctly.  They also display correctly in other 
fonts.

This seems to have started happening recently.

Anyone any ideas as to what is going on?

John