A Bounce

My PSA has gone up again, to about 1.8 (after a low in December 2007 of about 0.8). This seems to be a bounce. The doctors are telling me that this is unusual, and they are not sure what to make of it. If it goes over 2.0, they may want to do another biopsy. However, what I've read on the internet indicates that this is not uncommon. In any event, it is disconcerting.