Part of my answer to this question, unfortunately, is "next time you buy a dishwasher, don't buy this one!" I have now repaired mine about 4 times -- cleaned out everything, including the grinder, the filter, the spray arm, etc. I even bought & installed a replacement grinder (for $11.... not bad; you can buy them at places like Home Depot, Amazon, etc.). To unclog any obstructions I couldn't see, I poured in boiling water, vinegar and baking soda, as well as dishwasher cleaner from the local hardware store before running the cleaned machine.
Everything worked - temporarily. The fact is that this machine is not very well made. The plastic parts are light (in part, I assume, because it takes less energy to move them), but they are not durable. Also, newer dishwashers that are 'eco-friendly' save on energy by using less-hot water. Unfortunately, most powder dish detergents do not dissolve as well in cooler water as in hot water, so you get lots of caked-on detergent (in addition to the food and other gunk) blocking points of entry and exit.
A wet-dry vacuum cleaner is a handy thing to have while repairing this machine.