The 'balanced' mode isn't a guarantee that you'll be able to always have a move. It's not an 'endless' mode, nor was that my intention. You absolutely can still block yourself in, it's the nature of the game :)
One hint, if you're not already using it, is to make sure to use the 'wrapping' of the rows to your advantage -- they wrap left/right, and only fill with new blocks from the left side after making a column. Often you can save a run by setting up a leftmost or rightmost column over a couple turns.
