The default font used by kpresenter (Utopia [Adobe]) does not support the euro sign.
KPresenter requests the 8859-15 charset, so it looks like the glyph is simply
missing from the font, which is part of XFree86.
This bug has been reported several times now. These fonts do not contain
the Euro glyph. This is not a bug. If you want the euro, you must
choose a font which contains ISO8859-15 character set.
This is IMHO a bug in kpresenter, since choosing this font in xfontsel
does not show ISO8859-15.