I've noticed that it is apparently not possible to "unpick" lists in the Designer. The only way to "clear" the list is to select a field that has no (or cannot have, such as a line or box) list associated with it. This is at best annoyingly counterintuitive. As a side effect, a field which has been associated with a list will remain a list: it is as far as I can tell not possible to set it as a text field again even if there are no lists at all in the sheet.
Furthermore, the "Open list" of the Viewer has a bug (at least under my Windows XP build). It allows only one character to be typed (or only one use of the backspace key) before entering the data, and you have to reclick the field for every additional characters to be typed or sequence to be erased. This was noted and asked about back in February.