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1. Create a content type. Add a file field. Set the Widget Type to "Extensible File". Save the settings, and save the settings on the next page.
2. Navigate to node/add/[fieldname] -- the field created in Step 1 does not show up.
Setting the Widget Type to "File Upload" or "Image" (as this site has Imagefield installed) results in normal behavior -- the upload field displays.
I tested this in Garland, and in a custom theme we have built in-house, and the bug was present in both themes.