When adding action Overlay (wotermark) the preview image disappears

Hallo,
when I try to add action Overlay (wotermark) the preview image disappears and the png image as a wotermark can't be seen as well. On local host everything was working perfectly. But when I did the same on host this happens to me. Other octions work fine just the overlay actions doesn't work. Please could you give me a hint what do I do wrong or what should I set differently.

Thanks

Radek

here is export of actions I did:

$presets = array(); $presets['125x125_video_sipka'] = array ( 'presetname' => '125x125_video_sipka', 'actions' => array ( 0 => array ( 'weight' => '0', 'module' => 'imagecache', 'action' => 'imagecache_deprecated_scale', 'data' => array ( 'fit' => 'outside', 'width' => '125', 'height' => '125', ), ), 1 => array ( 'weight' => '0', 'module' => 'imagecache', 'action' => 'imagecache_crop', 'data' => array ( 'width' => '125', 'height' => '125', 'xoffset' => 'center', 'yoffset' => 'center', ), ), 2 => array ( 'weight' => '0', 'module' => 'imagecache_canvasactions', 'action' => 'canvasactions_file2canvas', 'data' => array ( 'xpos' => 0, 'ypos' => 0, 'alpha' => '100', 'path' => 'sipka.png', ), ), ), );