Candace,
I found the problem. In the "DynamicForms_DynamicQuestionEvent" database table, there was a row for the CheckBox Group question that, I believe, was giving the option of adding an "Other" item to the CheckBox Group in the event that one of the existing items was not adequate. I seem to remember at some point there being a setting in the Question setup that could be selected to allow users to enter an "Other" value, although I cannot seem to find it right now. Somehow during the course of editing the questions I must have taken off the "Other" option, but the row in the database table stayed put. Once I manually removed the row from the database table, the problem with the CheckBox Group went away.
However, the problem still persists with any Question Event that occurs; the Mask Edit fields show the masks until any Question Event fires. Once the Event occurs, and the Modal Popup disappears, all of the fields on the form which have masks, no longer display their masks.