Usually after 6-12 hours the drap and drop from Local to Remote Browser stops working and only the buttons in the middle panel work.
Double clicking on the file from local browser usually would open it for editing (.asp files) but when this happens the double click also stops working and when I do right mouse button over the file, the options that normally show are different. I use Textpad to edit ASP files, when SmartFTP is working properly I can see "Textpad" in the context menu on right mouse click, when the bug occurs, that option is gone and I think a few others too.
To solve it I must close SmartFTP and start it again then the problem is gone but it repeats eventually after many hours.
Looks like a real bug since the normal behaviour changes without any action being taken.