The short version is that the work to produce the "next" block depends on the previous block.  The moment a new block is found, any in-progress searching is aborted because it won't produce anything useful.  This is important because it encourages a "found" block to be used and distributed quickly.

You should see this message each time the litecoin network as a whole finds a new block.


it should be noted that p2pool has 10-second blocks so you'll see this message about once every 10 seconds.