turns out that OS X 10.8+ has an issue with a space in the directory name.
when you download mondosolitarie.wdgt.zip unzips into
"mondo solitaire.wdgt" - directory with a space in it
Just remove that space, e.g. -> mondo.wdgt or mondosolitaire.wdgt
and then install the widget - default game will be selected. Also selects for table, card, and card backs will be again available.
Enjoy
OS X 10.9