font in preference

Hello -

I've just started using MuseScore, and it's absolutely fantastic. However, I have an odd problem.

After using it for a couple of days, all of the text on the menu bar, and on the buttons on the palette, and all similar, rather seminal, text, has turned to a sort of non-font - sort of squares instead of letters.

I remembered where the preferences button on the drop-downs was, and went to that, but it won't let me change to a recognisable font, neither can I get at the reset defaults button.

When it first happened, I thought that I could just save my files, uninstall the software, and re-download it. I did this, and it's come back the same. I've purged the recycle bib, and anything else I could think of, and reinstalled again, but still the same problem.

I should add that this has not happened to any other programme, because I did initially think it was a computer or Vista problem.

Does anyone have any answers?

Thanks

Chris