Font size is too small

[Nons Joke]

Hi folks,

I've just installed GnuCash 1.8.10-12.
When I start it, the font size is absolutely unreadable, cause it's too small.
Is there a way to fix this ?

Here is the error I get in the shell :
The font "-adobe-helvetica-medium-r-normal--*-120-*-*-*-*-*-*" does not support
all the required character sets for the current locale "fr_FR at euro"
  (Missing character set "ISO8859-15")
  (Missing character set "ISO8859-15")
The font "-adobe-helvetica-medium-o-normal--*-120-*-*-*-*-*-*" does not support
all the required character sets for the current locale "fr_FR at euro"
  (Missing character set "ISO8859-15")
  (Missing character set "ISO8859-15")

Does this force GnuCash to use a default font ???

I post here a short config of my box :
- Debian Sarge 3.1 (kernel 2.4.27-2-386)
- Gnome version 64
- ScreenSize 1280*1024
- GnuCash 1.8.10-12

Thanks.