Weird admin behavior with custom fields on “new post”

I have a WordPress install (2.7.1) that is exhibiting some odd behavior on the “Add New Post” screen. The users of this install use two custom fields (‘url’ and ‘source’). When they go to add a new post, the section of the “Custom Fields” entry table includes a huge table of all their previously used values, each individual one in their own table row with name & value input fields. This large list precedes the “Add new custom field:” table with the key drop-down and the value textarea.

It’s hard to describe, so I’ve put a screen capture up:

http://www.capacityproject.org/wordpressissue.gif

We have many WordPress installs and this is the only one that exhibits this behavior. Anyone have any idea why WordPress would display the custom fields this way?

Best,

-Jeff