Diacritics problem

For a while now, all diacritics (like in French, etc. languages) in many progs on my xp sp1 os (OExpress, dictionaries, mirc) are rendered as cyrillic or even unknown letters (see jpg attachment). In IE options-fonts appears language script “cyrillic”. I change it to Latin based, click ok, but the Apply button is grayed out and if I clic ok again, on opening up again options-fonts, the language script is again cyrillic. What could cause this and how can I remedy it?
Thank you, P.

Anybody there? Gimme a hand, please…