Can you tell us more about your layout?
It sounds like you have two layout objects involved, but you have only told us about one: the drop down list. Is this field within a portal, a tab control or ??? In layout mode, when you draw a selection box around this field, do you see only one set of 4 selection handles appear?
A screen shot of this portion of your layout might (or might not) reveal something to us.
This layout has five tabs. On the tab where I have the problem there is a portal plus additional items on the screen. I have attached a screen shot of the field in question (Action towards the bottom of the screen). I also highlighted all the fields in that section of the form to see is there were more fields connected to it. I didn't see any.
I found the problem. I went to screen shot the Inspector, data tab and found I had the currency format applied versus the test format.