I think you'll have to post what the combos are based on (sql statements?). Not sure what 2 words means. Could be "this that" or "this, that" in which case you have a multi value field (not a great idea). You could also examine the row source property for each control - make a test query using their sql statements and look at them in design view for clues if your data is not in a multi value field. Whatever the criteria is, it doesn't work as you think.
EDIT - you also have to consider that the 2nd combo is filtered based on the bound column of the 1st combo - if the combo is bound. You might be seeing "this" in the control but if that isn't the bound column, the 2nd combo is basing the list on whatever is in the bound column of the 1st combo.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.