(why the issue was filed, steps to reproduce the problem, etc.)
Setup - I used a patched development version of Media and Media Gallery - see steps here: http://drupal.org/node/1244204#comment-6678836
Recreating the problem:
Error message "Warning: array_flip(): Can only flip STRING and INTEGER values! in DrupalDefaultEntityController->load() (line 178 of [site_docroot]/includes/entity.inc)."
This occurred because I deleted 3 pictures. The error message is displayed for each picture deleted. It does not display if you don't delete any of your pictures after uploading them. The error is displayed for both the authenticated user that can upload the gallery and also visible to unauthenticated users.
(description of the proposed solution, the rationale behind it, and workarounds for people who cannot use the patch)
It appears that deleting an image from a media_gallery gallery is not handled properly - I am guessing that some database entries relating to the deleted image are not removed or "cleaned up".
(reviews needed, tests to be written or run, documentation to be written, etc.)
Repeat steps that reproduced the problem, to see that the error message does not now appear (once the fix is done.)
User interface changes
(new or changed features/functionality in the user interface, modules added or removed, changes to URL paths, changes to user interface text)
The user should not need to do anything different when deleting an image.
(API changes/additions that would affect module, install profile, and theme developers, including examples of before/after code if appropriate)
Wouldn't expect any API to change, unless it is something still under development in Media 2.x-dev or Media Gallery 1.x-dev
Original report by [username]
// Text of original report here.
(for legacy issues whose initial post was not the issue summary)