On the form, I had an item whose response values are Yes, No, and Unclear, but the data saved/collected was only Yes and No. The problem was that I connected the item with a wrong table that contained response values. The steps I took to solve this:
a) I went to the tables that save data (x_table4 was the name in my application) and chose the design view. I clicked on the data type of the bad item and choose lookup wizard. This didn't work because the relationship was established already.
b) I went to the relationship cart by oging to Database Tools. I removed the relationship between the two tables, the table that contained the actual response values and the table that collected the data (x_table4). The wrong table containing response values was found, so I cut the link.
c) Now I went back to the design view of X_table 4. I do the same as described in step a. I go to the lookup wizard and connect the bad item with the table that contains the right choices.