Row weight changes from select list to text input when editing existing Context

System:
Drupal 7.14
Context 7.x-3.0-beta6
Chaos Tools 7.x-1.2

When editing an existing Context, and clicking the "show row weights" option, the element is rendered as a text input element rather than a select list.

<input id="edit-reactions-plugins-block-blocks-content-upper-bean-about-bosp-weight" class="tabledrag-hide form-text" type="text" maxlength="128" size="10" value="-10" name="reactions[plugins][block][blocks][content_upper][bean-about-bosp][weight]">

Additionally, the row weight is sometimes empty, sometimes set to the weight.

When adding a new context, the row weight is rendered as a select list:

<select class="tabledrag-hide form-select">

Tried changing to a different admin theme (Bartik) and the issue persists.

No error messages appear in the Drupal or server logs.

Kind of confused as to where this might be coming from, because I can't find an occurrence of a text input element in the context code anywhere.

Any suggestion of how to try to debug further would be appreciated.

Thanks!