gdImageStringFT: Could not find/open font while printing string p with font Arial

[oxy]

Hi,
the many posts on the net cannot help me solve the problem:

   gdImageStringFT: Could not find/open font while printing string p
with font Arial

when printing .png or .jpg plots on my octave-3.0.3 /
(Gnuplot 4.2 patchlevel 4)  on FreeBSD 6.4. EPS plots print fine.
I tried playing with the GDFONTPATH variable without success.

How to set GDFONTPATH if i have  for example
the following file which has a nice font?

  /usr/local/lib/X11/fonts/100dpi/helvBO08-ISO8859-15.pcf.gz

How to set GDFONTPATH in a more general way
including all /usr/local/share/fonts/cmpsfont and
/usr/local/lib/X11/fonts/75dpi  fonts?

Should i enter the following in octave for the font above?

set (0, 'defaulttextfontname', 'helvBO08-ISO8859-15.pcf');

Thanx ...