Cannot remove image, "no information available" in popup

When I click on the [Remove] button when editing a node that has an ImageField field in use, I get a confirm alert with the following text:

An error occurred.
/filefield/ahah/resources/field_resource_attachment/0
(no information available).

Where "resources" is my content types name, and "field_resource_attachment" is name of this field.

thanks,

jyg