Ktorrent doesn't let me to unselect/select files in the torrent when file list view is enabled in Files Tab

Seems to work fine here, when I click on an empty part of the view, the current selection is cleared.

Ok, I did two screenshoot hoping it may help you.
The frist one shows the files in tree view and not all them are selected to be downloaded.
In the second one all files are selected and if I click on checkbox, the check isnt removed or added but the changes I do are reflected on tree view and download size changes as it should.

That selection, was a bit confused, I thought you were talking about item selection in the file view.

Anyway you are right that was broken, I have just fixed it.