There's no real solution to the problem other than to remove the rating system entirely. Not only does it serve no purpose, but it misleads potential readers into believing a story is good or bad based on a metric that has been, and still is manipulated and abused by many.
By removing the rating system, potential readers will not merely glance at a story's rating to determine whether it is worth reading or not, but focus on the synopsis, proper reviews, and the first few chapters (which is how it should be, and is for some readers). It doesn't fix the problem, but it removes an avenue of abuse at least. And at least authors wont get hung up or bent out of shape over a bunch of 1 star ratings.
Without a rating system, griefers will need to write quality reviews whether they want to or not, since its easy for most to determine which review to believe in, one that says "This novel sux!" or "Though i enjoyed it initially, i liked it less and less as the story progressed. Here's why:".
The same also holds true for people lauding the awesomeness that is the novel they're reading. "Keep up the good work." is no longer a free 5 star rating, but merely a bit of encouragement for the author, one that doesnt tell anything to potential readers about the quality of the story, and thus should be ignored.