This is similar to QTCREATORBUG-31065

but is ocurring on windows.  Somehow mouse operations are not being tracked correctly in the dropdown so it becomes impossible to select a file.   Sometimes it works correctly, but first the mouse selection (higlighted) gets further and further from the mouse making it difficult to use.  Sometimes it is impossible to select the bottom item of the list.  Sometimes  it locks up completely and selection is impossible (solution exit qtcreator and start again).

Similarly to 31065 it occurs with a split screen.  Sometimes the LHS dropdown is fine, but the RHS dropdown is inoperable. 

I'd say this is new in QTCreator 14 and was not present in 13