Diacritic accents not displaying properly on Word

[alientango]

hello all
i would appreciate if someone could help solve this puzzle.

a month or so ago, everything worked fine with the diacritic accents on letters. since then, i have not touched Word, except to lend my Mac to a friend who needed to write her CV and letters.

for the last few days, i try to type like i normally do, with the accents, and for some reason, Word automatically changes the font into Monaco and it is impossible to format it into Times New Roman or anything else that isn't sans serif. this means i can change it to Helvetica, for example, or Gill Sans or Lucida Grande, but NOT, oddly, Arial.

what on earth happened?

is it a problem with my fonts? i recently downloaded some free fonts from the internet.

is it a problem with Word? did my friend perhaps unwittingly change something and now i don't know how to fix it?

is it possible to change the encoding in Word for a document (not a Web document)?

oh yes, input on the keyboard has remained the same, nothing has changed.

some info:
Mac OSX 10.4.11
1.33 GHz PowerPC G4
1 GB DDR SDRAM

i don't know what other info you might need but i'll try to supply if necessary.

can someone help please? i need to write my thesis!

thanks so much!