Scan for selected image file (same as for selected USB device) - close all possible confirmation dialogs, clear 'Image:' field and display popup 'file not found' error message if scanning for selected file failed.
I'm unclear on this. When do you think this should be done?
I don't know how monitoring of current drive in 'USB Device:' is implemented. It displays current drive - you remove it - and it disappears momentarily. Same can be implemented for current selected image file - if image file moved/renamed/became unavailable - do all the things from my prev comment. If it's possible only for USB drive - scan for current image file can be done with some repetitive delay - like scan every 1 or 2 or 3 seconds.
okay dokay