Hi again, I think this time I found a real BUG.
In theory, it could be related to the fact that I live in a country where I am automatically disconnected from the net after 24 hours.
When I leave SlskQt running for QUITE awhile ( = 8 hours doing nothing, e. g. in the night), and get up in the morning and try to re-run the search (using the handy (!) context menu entry provided), there will be ** no results at all **.
The "fix" is to simply disconnect from the slsk network and reconnect again. Suddenly, my search results are filled up to the brim again.