gs: not found Image Magick

[mappolonia at appolosecure.com]

I can execute Image Magick convert PDF to jpg from shell with no problem.  If I try from PHP script, like this:

<?
exec("/usr/local/bin/convert test.pdf test.gif");
?>

I get the following errors:

gs: not found
convert: Postscript delegate failed `test.pdf'.
convert: missing an image filename `norden.gif'.

If I try to convert non-pdf files in php script, it works OK.

Any help would be great!