Enclosure Custom Fields Deleting!

Recently upgraded WordPress to 2.8.1 and since then have had this problem.

I’ll add the custom field “enclosure” for our podcast files with normal structure, but after the post is updated and I refresh the editor or go and look at the post page, the field’s been deleted!

This only happens with the field “enclosure”. Other fields I’ve tried don’t have no problem.

I’ve upgraded and deactivated all plugins. I’ve heard that this is a conflict with the Podpress or Podcasting plugins but neither of those are or have ever been activated.

Ideas? Kind of urgent issue here as this is a high volume site with a bunch of podcasts… thanks!