Error occurred while uploading image in clustered environment

Server 1 says:

2009-12-17 14:50:23,063 ERROR [org.hippoecm.frontend.plugins.gallery.GalleryWorkflowPlugin] Unable to update item: node /: bec8ae1e-71a3-42ab-b5e5-599fc7d7e532
2009-12-17 14:50:23,078 WARN [org.hippoecm.frontend.JcrObservationManager] Unable to add child node to list: e4ee203a-1682-480f-9a9e-4ba06647994a

A couple of seconds later server 2 says:

2009-12-17 14:51:06,718 WARN [org.hippoecm.repository.security.HippoAccessManager] Unable to find node id, allowing read permissions: Unable to resolve the node id from the path /content/gallery/images/regeringspagina/kabinetten sinds 1945/kab_lubbers3_89.jpg[2]/kab_lubbers3_89.jpg/myproject:thumbnail/jcr:data
2009-12-17 14:51:06,719 WARN [org.hippoecm.repository.security.HippoAccessManager] Unable to find node id, allowing read permissions: Unable to resolve the node id from the path /content/gallery/images/regeringspagina/kabinetten sinds 1945/kab_lubbers3_89.jpg[2]/kab_lubbers3_89.jpg/myproject:thumbnail/jcr:mimeType
2009-12-17 14:51:06,719 WARN [org.hippoecm.repository.security.HippoAccessManager] Unable to find node id, allowing read permissions: Unable to resolve the node id from the path /content/gallery/images/regeringspagina/kabinetten sinds 1945/kab_lubbers3_89.jpg[2]/kab_lubbers3_89.jpg/myproject:picture/jcr:data
2009-12-17 14:51:06,719 WARN [org.hippoecm.repository.security.HippoAccessManager] Unable to find node id, allowing read permissions: Unable to resolve the node id from the path /content/gallery/images/regeringspagina/kabinetten sinds 1945/kab_lubbers3_89.jpg[2]/kab_lubbers3_89.jpg/myproject:picture/jcr:lastModified
2009-12-17 14:51:06,719 WARN [org.hippoecm.repository.security.HippoAccessManager] Unable to find node id, allowing read permissions: Unable to resolve the node id from the path /content/gallery/images/regeringspagina/kabinetten sinds 1945/kab_lubbers3_89.jpg[2]/kab_lubbers3_89.jpg/myproject:picture/jcr:mimeType
2009-12-17 14:51:06,719 WARN [org.hippoecm.repository.security.HippoAccessManager] Unable to find node id, allowing read permissions: Unable to resolve the node id from the path /content/gallery/images/regeringspagina/kabinetten sinds 1945/kab_lubbers3_89.jpg[2]/kab_lubbers3_89.jpg/myproject:picture/jcr:primaryType
2009-12-17 14:51:06,719 WARN [org.hippoecm.repository.security.HippoAccessManager] Unable to find node id, allowing read permissions: Unable to resolve the node id from the path /content/gallery/images/regeringspagina/kabinetten sinds 1945/kab_lubbers3_89.jpg[2]/kab_lubbers3_89.jpg/myproject:picture