<<<< I don't have the same specific problem as you, but there is for sure something strange with the Dialog as this problem occurs through-out. My problem is that the file indexing seems to be dropped and re-cached every time that the Dialog is used. It might be a related problem. Have you tried letting it stand for a few minutes to see if it re-appears ?

Dialog box is well openning but don't give the time to choice a file (any place is it, test, desktop or user directory), dialog box is closing.
Apprently dialog box is well closing and is not hidden behind the MOi Ui.