convert: unable to open image `convert'

Just start using this module with PDF to ImageField module.
After little experimenting everything start work as we expect, but still receive error.

ImageMagick error 1: convert: unable to open image `convert': @ error/blob.c/OpenBlob/2489. in _imagemagick_convert_exec() (line 519 of

In Image toolkit (admin/config/media/image-toolkit) this appear:

Debug: ImageMagick command:
/usr/bin/convert -version
in _imagemagick_convert_exec() (line 495 of /home/office4s/public_html/sites/all/modules/imagemagick/imagemagick.module).
Debug: ImageMagick output:
Version: ImageMagick 6.6.0-2 2010-04-14 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2010 ImageMagick Studio LLC
Features: OpenMP

Debug: ImageMagick command:
/usr/bin/convert -version
in _imagemagick_convert_exec() (line 495 of /home/office4s/public_html/sites/all/modules/imagemagick/imagemagick.module).
Debug: ImageMagick output:
Version: ImageMagick 6.6.0-2 2010-04-14 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2010 ImageMagick Studio LLC
Features: OpenMP

in _imagemagick_convert_exec() (line 497 of /home/office4s/public_html/sites/all/modules/imagemagick/imagemagick.module).
The configuration options have been saved for all domains.
Debug: ImageMagick command:
/usr/bin/convert -version
in _imagemagick_convert_exec() (line 495 of /home/office4s/public_html/sites/all/modules/imagemagick/imagemagick.module).
Debug: ImageMagick output:
Version: ImageMagick 6.6.0-2 2010-04-14 Q16 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2010 ImageMagick Studio LLC
Features: OpenMP

in _imagemagick_convert_exec() (line 497 of /home/office4s/public_html/sites/all/modules/imagemagick/imagemagick.module).

I am not sure that the error is coming from this module or from imagecache where we continue recevie follow error:
convert: unable to open image `convert': @ error/blob.c/OpenBlob/2489.

User error: ImageMagick error 1: convert: unable to open image `convert': @ error/blob.c/OpenBlob/2489. in _imagemagick_convert_exec() (line 519 of /home/office4s/public_html/sites/all/modules/imagemagick/imagemagick.module).
User error: ImageMagick error 1: convert: unable to open image `convert': @ error/blob.c/OpenBlob/2489. in _imagemagick_convert_exec() (line 519 of /home/office4s/public_html/sites/all/modules/imagemagick/imagemagick.module).
User error: ImageMagick error 1: convert: unable to open image `convert': @ error/blob.c/OpenBlob/2489. in _imagemagick_convert_exec() (line 519 of /home/office4s/public_html/sites/all/modules/imagemagick/imagemagick.module).
User error: ImageMagick error 1: convert: unable to open image `convert': @ error/blob.c/OpenBlob/2489. in _imagemagick_convert_exec() (line 519 of /home/office4s/public_html/sites/all/modules/imagemagick/imagemagick.module).
User error: ImageMagick error 1: convert: unable to open image `convert': @ error/blob.c/OpenBlob/2489. in _imagemagick_convert_exec() (line 519 of /home/office4s/public_html/sites/all/modules/imagemagick/imagemagick.module).
User error: ImageMagick error 1: convert: unable to open image `convert': @ error/blob.c/OpenBlob/2489. in _imagemagick_convert_exec() (line 519 of /home/office4s/public_html/sites/all/modules/imagemagick/imagemagick.module).
User error: ImageMagick error 1: convert: unable to open image `convert': @ error/blob.c/OpenBlob/2489. in _imagemagick_convert_exec() (line 519 of /home/office4s/public_html/sites/all/modules/imagemagick/imagemagick.module).
User error: ImageMagick error 1: convert: unable to open image `convert': @ error/blob.c/OpenBlob/2489. in _imagemagick_convert_exec() (line 519 of /home/office4s/public_html/sites/all/modules/imagemagick/imagemagick.module).
Notice: Undefined index: filefield_sources in filefield_sources_field_process() (line 132 of /home/office4s/public_html/sites/all/modules/filefield_sources/filefield_sources.module).