Cursor "curItemData" is created before that code runs. Everything is fine for a first time. Second time I run this code I am getting an error:
Alias 'CURITEMDATA' is not found. ....cbodefects.ControlSource 0

Are you rebuilding curItemData on the fly? If so, see this article for a technique to rebuild your cursor without closing it: http://weblogs.foxite.com/andykramek/archive/2005/03/19/174.aspx. Then, after you rebuild curItemData using this technique, requery() your combo box.