Unable to get Gallery image block

My Configartion:
drupal 4.7rc3
gallery 2.1.1a
gallery module 4.7.0 19.4.2006

After installing and configuring the gallery and the image block everything is working fine without problems.

Then after hours without changing anything in the gallery or my drupal site, i got the error:
Unable to get Gallery image block.
Then i'm changing around the gallery image block settings to get the block work again. Sometimes i have to go to the standalone-gallery, and then changing image block settings.
There is no rule what i have to change.
After this succeded configuration, the block is working again for some hours .... then i get: "Unable to get Gallery Image Block" and so on:

Thanks
JumpingJack

Watchdog:
Unable to get Gallery image block
Error (ERROR_CONFIGURATION_REQUIRED)
in modules/core/classes/GalleryEmbed.class at line 851 (gallerycoreapi::error)
in /www/htdocs/v034616/drupal47/modules/gallery/gallery_block.inc at line 110 (galleryembed::getimageblock)
in /www/htdocs/v034616/drupal47/modules/gallery/gallery.module at line 186
in ??? at line 0
in /www/htdocs/v034616/drupal47/includes/module.inc at line 185
in /www/htdocs/v034616/drupal47/modules/block.module at line 638
in ??? at line 0
in /www/htdocs/v034616/drupal47/includes/module.inc at line 185
in /www/htdocs/v034616/drupal47/includes/theme.inc at line 937
in ??? at line 0
in /www/htdocs/v034616/drupal47/includes/theme.inc at line 166
in /www/htdocs/v034616/drupal47/themes/engines/phptemplate/phptemplate.engine at line 164
in ??? at line 0
in /www/htdocs/v034616/drupal47/includes/theme.inc at line 166
in /www/htdocs/v034616/drupal47/index.php at line 29