Error resizing image using minimagick

Hi.

I’m uploading images using a standard form. A thumbnail is made using
minimagick, when I upload files larger than 2 MB I get this error:

ImageMagick command (mogrify -resize 500x500 /tmp/minimagic15697.0)
failed: Error Given 256

Images smaller than 2 MB works fine. Is there some configuration I need
to do?

regards
Claus