If in the puzzle list I only check "unsolved puzzles", press select, and then click on one of the column headers of the puzzle list, "unsolved puzzles" gets unchecked and the list of puzzles becomes empty.
This is an issue that was pointed out to us before, but we haven't repaired it yet. You can get around it by always collapsing the selection-menu's after picking your favourite options, by clicking on the [-] button, before pressing the [select] button.