[magick-users] Problem converting PDFs after changing web hosts

[George Mouchet]

I changed web hosts and now when I try to make a jpeg thumbnail from a pdf,
some of the images come out black.  In the attached files, preview.jpg is
the problem file from the new host and preview_from_old_host.jpg is the one
from the old host.  My imagemagick command is:

 

convert 02a.pdf[0] -resize 350X450 -quality 70 -colorspace RGB preview.jpg

 

The new web host seems to be clueless.  What could be causing the problem?
How can I diagnose it?