Why are nodes not saving, and redirecting to edit instead?

Question

When editing a node and attempting to saving it, the user is redirected to the edit form with no error message and the node is not updated. This situation is similar to the problem described in "Nodes do not save, but instead redirect to edit page again", but in Drupal 6 and in all content types. The nodes have at least one field, FileField, which is common to all nodes but I haven't had any problem with it in other sites. There're no errors, nothing in the logs. I'm clueless.

Edit: I've identified that the problem is with content types that have a FileField field. Sadly, I still don't have a clue of what could be causing the problem.

Answer 1

It was the FileField that was causing the problem. I still don't know why but I removed it and the node could be saved again.

Edit: It seems the problem is caused by CCK fields. Nodes without CCK fields are not experiencing this problems.