Failed image upload makes it impossible to update/save node

When uploading multiple pictures via the image_field sometimes an upload will fail (timeout or similar).A problem then sometime arise when trying saving/updating the node afterwards (I am most often able to reproduce this issue when I am trying to upload many pictures to a gallery):

• Firstly, Drupal now gives the error "Undefined index: display_field in file_field_widget_value() (line 582 of modules/file/file.field.inc)"
• Closing the failed node-edit session and clicking edit again causes the following errors when trying to add new content
• If the image field is mandatory, Drupal will complain that you did not fill out the field while trying to upload an image through the field
• If the image field is not mandatory, Drupal will complain that "The content on this page has been modified by another user" and will not save changes
• Whenever trying to add new pictures Drupal will say "Node updated" after each upload, but nothing is saved, and pressing save button will cause the "The content on this page has either been modified by another use" error

I have experienced this problem with several Drupal 7.0 and Drupal 7.12 installations, but it mostly comes +30 pictures. I have tried the following with no luck:

• Logging out and resetting cache as soon as upload fail
• Truncating the form_cache table
• Trying to remove all traces of the failed upload from the following tables: file_usage, file_managed, field_revision_field_image, field_data_field_image