Dynamically created DropDownList loses ListItems on Postback

I have a page that contains some dynamically created controls (TextBox and DropDownList). When a postback occurs, the TextBoxes keep their values, but the DropDownLists lose their ListItems.
This is quite confusing, since the page level DropDownList also keeps its ListItems. Can anyone see what’s wrong with the code below?

asp dropdownlist dynamic value from javascript issue

I have a dropdownlist with 5 items. Value of last item is “other”. By choosing “other” appears popup with input. The value of this input i set to this item by javascript. So value becoms inserted text. When i submitting the form, it doesn’t work with this dynamic value, but other items of select works. Any ideas? Thanks very much!