Can't load images

Hi there.
I'm a newbie to Omeka, and can't load images. I've run the "Test" in Settings and I get the following error:
exception 'Omeka_File_Derivative_Exception' with message 'Failed to execute command: /usr/bin/convert -version.' in /home/rusde260/public_html/application/libraries/Omeka/File/Derivative/Strategy/ExternalImageMagick.php:212
Stack trace:
#0 /home/rusde260/public_html/application/libraries/Omeka/File/Derivative/Strategy/ExternalImageMagick.php(165): Omeka_File_Derivative_Strategy_ExternalImageMagick::executeCommand('/usr/bin/conver...', NULL, NULL, NULL)
#1 /home/rusde260/public_html/application/controllers/SettingsController.php(204): Omeka_File_Derivative_Strategy_ExternalImageMagick::isValidImageMagickPath('/usr/bin')
#2 /home/rusde260/public_html/application/libraries/Zend/Controller/Action.php(516): SettingsController->checkImagemagickAction()
#3 /home/rusde260/public_html/application/libraries/Zend/Controller/Dispatcher/Standard.php(308): Zend_Controller_Action->dispatch('checkImagemagic...')
#4 /home/rusde260/public_html/application/libraries/Zend/Controller/Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http))
#5 /home/rusde260/public_html/application/libraries/Zend/Application/Bootstrap/Bootstrap.php(105): Zend_Controller_Front->dispatch()
#6 /home/rusde260/public_html/application/libraries/Zend/Application.php(384): Zend_Application_Bootstrap_Bootstrap->run()
#7 /home/rusde260/public_html/application/libraries/Omeka/Application.php(79): Zend_Application->run()
#8 /home/rusde260/public_html/admin/index.php(28): Omeka_Application->run()
#9 {main}

The error I get when I try to add a file to an item is the following:

Omeka_File_Derivative_Exception
Failed to execute command: /usr/bin/convert '/tmp/8d161f2a90b686002d791a4fe8561aac.jpg[0]' -background white +repage -flatten -thumbnail '800x800>' '/tmp/fullsize_8d161f2a90b686002d791a4fe8561aac.jpg'.

exception 'Omeka_File_Derivative_Exception' with message 'Failed to execute command: /usr/bin/convert '/tmp/8d161f2a90b686002d791a4fe8561aac.jpg[0]' -background white +repage -flatten -thumbnail '800x800>' '/tmp/fullsize_8d161f2a90b686002d791a4fe8561aac.jpg'.' in /home/rusde260/public_html/application/libraries/Omeka/File/Derivative/Strategy/ExternalImageMagick.php:212
Stack trace:
#0 /home/rusde260/public_html/application/libraries/Omeka/File/Derivative/Strategy/ExternalImageMagick.php(49): Omeka_File_Derivative_Strategy_ExternalImageMagick::executeCommand('/usr/bin/conver...', NULL, NULL, NULL)
#1 /home/rusde260/public_html/application/libraries/Omeka/File/Derivative/Creator.php(76): Omeka_File_Derivative_Strategy_ExternalImageMagick->createImage('/tmp/8d161f2a90...', '/tmp/fullsize_8...', 'fullsize', 800, 'image/jpeg')
#2 /home/rusde260/public_html/application/models/File.php(356): Omeka_File_Derivative_Creator->create('/tmp/8d161f2a90...', '8d161f2a90b6860...', 'image/jpeg')
#3 /home/rusde260/public_html/application/models/Job/FileProcessUpload.php(22): File->createDerivatives()
#4 /home/rusde260/public_html/application/libraries/Omeka/Job/Dispatcher/Adapter/Synchronous.php(25): Job_FileProcessUpload->perform()
#5 /home/rusde260/public_html/application/libraries/Omeka/Job/Dispatcher/Default.php(136): Omeka_Job_Dispatcher_Adapter_Synchronous->send('{"className":"J...', Array)
#6 /home/rusde260/public_html/application/models/File.php(203): Omeka_Job_Dispatcher_Default->send('Job_FileProcess...', Array)
#7 [internal function]: File->afterSave(Array)
#8 /home/rusde260/public_html/application/libraries/Omeka/Record/AbstractRecord.php(277): call_user_func(Array, Array)
#9 /home/rusde260/public_html/application/libraries/Omeka/Record/AbstractRecord.php(550): Omeka_Record_AbstractRecord->runCallbacks('afterSave', Array)
#10 /home/rusde260/public_html/application/models/Item.php(335): Omeka_Record_AbstractRecord->save()
#11 /home/rusde260/public_html/application/models/Builder/Item.php(204): Item->saveFiles()
#12 /home/rusde260/public_html/application/libraries/globals.php(567): Builder_Item->addFiles('Upload', 'file', Array)
#13 /home/rusde260/public_html/application/models/Item.php(320): insert_files_for_item(Object(Item), 'Upload', 'file', Array)
#14 /home/rusde260/public_html/application/models/Item.php(230): Item->_uploadFiles()
#15 [internal function]: Item->beforeSave(Array)
#16 /home/rusde260/public_html/application/libraries/Omeka/Record/AbstractRecord.php(277): call_user_func(Array, Array)
#17 /home/rusde260/public_html/application/libraries/Omeka/Record/AbstractRecord.php(531): Omeka_Record_AbstractRecord->runCallbacks('beforeSave', Array)
#18 /home/rusde260/public_html/application/libraries/Omeka/Controller/AbstractActionController.php(229): Omeka_Record_AbstractRecord->save(false)
#19 /home/rusde260/public_html/application/controllers/ItemsController.php(91): Omeka_Controller_AbstractActionController->editAction()
#20 /home/rusde260/public_html/application/libraries/Zend/Controller/Action.php(516): ItemsController->editAction()
#21 /home/rusde260/public_html/application/libraries/Zend/Controller/Dispatcher/Standard.php(308): Zend_Controller_Action->dispatch('editAction')
#22 /home/rusde260/public_html/application/libraries/Zend/Controller/Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http))
#23 /home/rusde260/public_html/application/libraries/Zend/Application/Bootstrap/Bootstrap.php(105): Zend_Controller_Front->dispatch()
#24 /home/rusde260/public_html/application/libraries/Zend/Application.php(384): Zend_Application_Bootstrap_Bootstrap->run()
#25 /home/rusde260/public_html/application/libraries/Omeka/Application.php(79): Zend_Application->run()
#26 /home/rusde260/public_html/admin/index.php(28): Omeka_Application->run()
#27 {main}

Any help would be greatly appreciated.
Cheers
Dave

I'm guessing that imagemagick is either not installed, or is installed somewhere there Omeka can't find it. That'd be a question for your server admin.

You might also try the GD strategy for creating thumbnails as described here.