Dishwasher draining

all of a sudden the dishwasher shoots water up through the vent that is mounted in my kitchen sink. All these years it has just been there, now it profusely shoots water out. We changed the garbage disposal, checked for clogs, unscrewed the vent and checked for clogs and we cant figure out what is happening. Please help.

i used to work for a washing machiene company, I had it where when the wasing machiene emptied water came up through te sink outlet, it turned out to be a blockage on the sink outlet / pipe to waste.

You did say you checked for blockages but whatabout the sink pipes? since it is unlikely that your dishwasher is pumping water out any faster than it used to it would point to a blockage else where, as the water can not get out quick enough