I have three combo boxes, all behaving in the same manner.
Code is on Entry...PopUp box comes up as desired, values are shown as desired, selection is made, and combo box is filled with garbage.

Here is an image of OnEntry to the empty element:


Here is an image after selection was made, any choice gives similar results:


Here is the code:

IF @ISBLANK(GradedBy) THEN {
	POPUPSELECTPOSITION(4, @XPos(GradedBy), @YPos(GradedBy))
	GradedBy = @USERSELECT("SL,CJ,CD,LK,NB")
	} 

If I copy and paste the resulting value, this is the typical result, alpha characters with CTL chars:
~^A^K^I^CSE
The resulting value is saved in the table, not the selected value.
Combo Box has same values in ToolTip and Restricted properties as listed for the PopUp list.

Any idea on what is happening?

Are you using ComboBox with UserSelect? I thought Userselect will be used with text box otherwise it will be duplicating the functions of providing list for selection.  Do you have any list in the Combobox for selection?