This is what happened recently on one of our drupal 7 website:
Problem:
Content body (node description) disappeared for all content types. Content body was present in the database but it was not displayed on website.
Solution:
After lot of debugging and searching we found a related post: http://drupal.org/node/989540
Hence I fired below queries:
UPDATE node SET language = ‘und’;
UPDATE field_data_body SET language = ‘und’;
UPDATE field_revision_body SET language = ‘und’;
We were not sure how we ended up with this problem, but it might have to do something with locale module. But above queries fixed our problem
Hope it helps.