@Linkat,
You can check the condo association bylaws, but I doubt that there's anything in there about the unit owners overturning a decision by the board.
Usually, if there are large one-time expenses, a condo board will vote for a special assessment, not an increase in the regular assessment. That's unusual, but it's not beyond the board's authority. Your best option, then, is to vote out the current board members at the next election and install a board that will roll back the fee increase.