But if there is an 1 empty space, the last jump may be made into that space, colapsing the row - leaving the board full with no spaces (since the jumping frog took the last open space)

Oh, I see what you are saying - there will be an empty row on the outside where the board just shifted from. In my mind, I did not think of those as empty rows - just that the board actually got smaller. (but would probable be easier to program and such if it was considered an empty row.

Then a rule would have to be put into place that all shifts go right or down. :-)