Megawizard FIFO problem: Write and read request filling FIFO!

Bizarre indeed. Note that your read/write counters always increment, and the used words is just the difference between the two. Is it possible that, without protection circuitry, you've read past empty or written past full? This basically gets your counters to flip around each other, and so a read no longer moves the read counter toward your write counter(making the difference, rdusedwds get smaller), but it would be moving the read counter further away, making it get larger?