[XeTeX] Problem with tremas

[Marc Pautrel]

Hi,

I use XeTex 0.993 + TeXShop 2.09 on PPC 10.4.6.

My text is in UTF-8 but I cannot obtain the trema letters in french : i,
e, u, o even with the \"{i} or \"i.

When I enter the i trema in TexShop, it displays correctly in the TeX
source, but it produces a blank square in the PDF.

When I enter \"{i} or \"i in TexShop, it displays correctly in the TeX
source, but it produces i *without* trema in the PDF.

Do you know how I can fix that ?

Thanks

MP